Math Secrets | Kevin Ventura | Skillshare

Math Secrets

Kevin Ventura

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7 Lessons (53m)
    • 1. Intro

      3:24
    • 2. Mental Math secrets

      12:07
    • 3. Quickly Add Single Digit Numbers

      6:08
    • 4. Quickly Add Double Digit Numbers

      8:20
    • 5. Multiplying 2 digits by 1

      4:34
    • 6. Multiplying 2 digits by 2

      9:11
    • 7. Multiply Any Number by 11

      9:32
15 students are watching this class

About This Class

Welcome to mental math secrets

I want to thank you for taking the time to visit, a place where you will be learning all about mental math secrets.

What is mental math secrets?

Mental Math secrets is a variety of math techniques that will help you solve math problems like you’ve never been able to solve them before.

What you will be learning by taking this course: 

  • The most important mental math secret

  • How to quickly add single column problems

  • How to quickly add double digit column problems

  • How to quickly multiply 2 digit numbers

  • How to quickly multiply 2 digit numbers by 2 digit numbers

  • How to multiply any number by 11.

The best and most important part is that after taking this course you wont need a pencil and paper to solve basic math problems, I look forward to showing you my mental math secrets so enroll in the course now and lets get started.

Transcripts

1. Intro: welcome to mental math secrets. My name is Kevin Ventura, and I'm gonna be your instructor for this course. I am extremely excited to share with you all of the mental math secrets that I've learned throughout my years as a student and math tutor. So why learn mental math secrets? Great question. The truth is, we all need and the pendulum numbers from that they were born. They're part of our everyday lives in the ways you probably didn't even think about or notice. Think about a conversation you might have had with a friend on the phone. You needed a phone number to call your friend, and the time you spend on the phone was measured in numbers as well. In the form of seconds, minutes and hours. Numbers have many forms. Let's think about every single date in history that has ever occurred, whether it's important or not, or even the most important day of your life. Your birthday is measured in numbers, one of the most important, and I say important because of how much it influences us. Whether you're in a little or a young teen and it's only dependant on numbers is money. We use money to place value on things and to purchase items and the language, which all these numbers communicate. In his math, most of us know the basics of math, adding, subtracting, multiplying and dividing. And when doing math, most of us needed pencil paper or a calculator to make even the most basic calculations. But what if I told you I can teach you how to make such calculations in your mind with the mental math secrets you'll learn in this course? I remember when I first learned some of the mental math tricks you learned in this course, my friends would test me or ask me to help them solve basic math problems, which made me feel amazing immediately knowing the answer when they asked. Another advantage of knowing mental math secrets is during math exams like the S A. T s, which is time sensitive. You'll be able to speed through the problems with the mental math tricks I'll be teaching you in this course. So what are some of the topics will be exploring in this course. First, I will be letting you went on one of the most important mental math secrets you could learn which will make you look like a math genius. When people ask you math questions, then we will be learning how to quickly add single digit numbers, followed by adding double digit numbers in your mind without the need of a pencil or paper . We will then move on to our second section, where you will truly see the power of mental math. We will start by multiplying two digits by one, followed by multiplying two digits by two digits. And finally, we will learn how to multiply three digit numbers quickly in our mind. So are you ready to become a mathematician and take your math skills to the next level? Come and join me, and in less than one hour, I can assure you you'll be amazed the calculations you can make in your head without the need of a pencil and paper and most of all, a calculator. I want to thank you for watching this video, and I look forward to working with you 2. Mental Math secrets: What is the number one secret to mental math? The number one secret to mental math is knowing your compliments. You may ask yourself, what do you mean by annoy your compliments, But I can assure you you already know what they are. You just may not know that they're referred to West compliments. So what are compliments? Let me show you a few examples so that you can see what I mean. For example, the complement of number two is number eight. Another example would be the complement of number one is number nine. Immediately, you could start to see a pattern of what a compliment is. A compliment is basically, when you have a number, for example, the number two. What other number can you add to the number two to give you 10? The answer is eight. Because of you, add two plus eight. You'll get 10 in our second example where we have number one, we know that nine will help us get 10. Let's do a few more as an exercise, and you'll start to see how annoying your compliments will help you add and subtract at lightning speed with the tricks you learn in this course. Next let's say we have number three. What number would you need? Or, in other words, what plus three gives you 10. The interest seven. Because three plus seven is 10. Next we have five. And that may be an easy one because we know five plus five is 10. Next we have four. And we ask ourselves, what number plus four do we need to give us 10? The answer is six because four plus six is ton. Next. What is the complement of seven? We know that three plus seven is ton, so we know that the answer is three. Because we did that earlier. Sold the numbers air just reverse the same way you may encounter them in the real world. Next, what is the complement of eight? Their answers to because eight plus two is 10. Next. What is the complement of six? Earlier we said four plus six is 10. So are an interest. Four. Because six plus four equals 10 as well. And last but not least, what is the complement of nine? That's an easy one, since we know that adding 1 to 9 gives us 10 and just to get the hang of our compliments of 10. Let's redo what we just did. But this time I'll ask and wait a second and you answer before I give you the answer, because that's how you'll be able to do. Rapid mental math is by practicing. Let's start with the number one. What is the complement of one? The answer is lined because nine plus one equals 10. Next, what is the complement of to the answer is eight. Next? What is the complement? Off number three? The answer is seven. Next. What is the complement of four? The answer is six. What is the complement? Off number five? The answer is five. Next. What is the complement? Off number six? The answer is four. Next. What is the complement of number seven? The answer is number three. Next. What is the complement? Off number eight? The answer is number two. Next. What is the complement? Off number nine? The answer is one great. This time around, I'm sure you were able to reach the answer easier, because by practicing your mind is able to figure out the answer quicker. Next, let's look at a few examples of the compliments of the number 20 first. Let's look at the number 11. What is the complement of 11? In other words, what plus 11 will give us 20? The answer is nine. Next. What is the complement of 17? The answer is three because 17 plus three is 20. Next. What is the complement? Off? 14. The answer is six because six plus 14 equals 20. Next. What is the complement? Off? 16. The answer is four. Next. What is the complement of 12? The answer is eight because 12 plus eight equals 20. Next. Let's look at a few examples off the compliments off 40. And to conclude this video, we will look at the compliments of Ah 100 you'll start to see the true power of mental math . But first, what? Plus 25 is going to give us 40? The answer is 15 because 25 plus 15 is 40. Next. What is the complement? Off? 31. The answer is nine because 31 plus nine is going to give us 40. Next. What is the complement? Off? 37. The answer is three because 37 plus three is 40 and one more example off the compliments of 40 22. What plus 22 can give us 40. The answer is 18 because 22 plus 18 is 40. Great. I know you're probably wondering why or what is the point of knowing your compliments? And that's a very good question to ask yourself, because when we get into a long column addition and subtraction, you'll see how you can easily add or subtract a bunch of numbers by simply looking at them . Before we conclude this video, we're going to take a look at the compliments of 100 this is one of the many mental math secrets that will help you solve problems quickly and easy. This is one of the first tricks I learned, which only made me more excited about learning more mental math secrets, which I will be sharing with you throughout this course. First, let's stick it to get the number 45. If I ask you what, plus 45 will give you 100. One way you can do that is by subtracting 45 from 100 you get the answer. But most likely you need a pencil and paper to do that math Instead, I will show you a trick. I learned that only requires you do very basic addition to each of the numbers separately. So, for example, the number on the right in this case, five. All you need to do is at a number to it that is going to make equal to 10 and the number on the left. And this case for all you need to do is add a number to it that will make it equal to nine . I know that may sound a bit confusing, so let me show you what I mean. Remember I said that the number on the right requires you add a number to it that is going to make it equal to 10. So in this case, all you have to ask yourself is what? Plus five is going to give me 10. We did our compliments earlier, so we know that five plus five is ton, so we know that we need five. So let's write that down. Next. We look at our next number four and earlier we said we need to add a number that will make it equal tonight. So we ask ourselves what? Plus four equals nine, and the answer is five because four plus five is nine. And there we have our answer. 55 and to reiterate, Let's look it. Our right column equals 10 and our left column is supposed to equal nine. And if we add 45 plus 55 that will give us 100. I know that maybe a lot of steps. I remember the first time I learned this trick. I just said to myself, What just happened? But let's look at a few more so that you know what I mean. And you can do this on your own when trying to figure out compliments of 100. Next, let's look at the number 73. Remember we said the number on the right When he died, a number to it. There were a result in 10 and the number on the left. We need Adam, number two it that will result in nine. So let's look back at our first number on the right and ask what? Plus three will give us turn and we know the answer is seven. Because we that our complements for leader. So let's write that down. Next we look at the number on the left and ask what? Plus seven is going to give us nine because the number on the left needs to always equal nine. And the answer is to. And now we know our answer is 27 and we know it's 27 by making sure the column on the right equals ton and the column on the left equals nine. And if we add 73 plus 27 we'll see. It gives us 100. Great. I hope you're starting to see that With this simple mental math trick, you can determine the compliments of 100 by simply doing basic addition with the number on the right and the number on the left. Let's do one more, because this is how you become greater. Anything in life, especially with math, is by practicing over and over to your mind. Becomes familiar with it, and it sort of becomes second nature. Let's look at the number 67. First we look at the number on the right and ask what plus seven equals turn. The answer is three. Next we look at the number on the left and ask what plus six will give us nine. The answer is three as well, and now we know our answer is 33. And to double check. Let's make sure that the right equals 10 and the column on the left equals nine. And if we add 67 plus 33 that's going to give us 100. Great. I hope you were able to see that by doing simple addition. With the number on the right and the number on the left, you can determine the compliments of 100. The only time it doesn't work is with multiples of 10 like if you have the number 20 or if you have the number 50. But any other numbers that don't end with zero. You can use this mental math trick and figure out how far any number is from 100. This is going to conclude this video on mental math secrets. On our next video, we will start to really kick things into high gear and learn how to rapidly at a single column of numbers. I want to thank you for watching this video, and if you have any questions, please don't hesitate to ask. Thanks 3. Quickly Add Single Digit Numbers: Hey, everyone, welcome back. In our last video, we explored the concept of compliments. In this video, we will start to see why and how it is useful. Annoy your compliments when adding a long column of numbers Far First problem. Let's take a look at two plus three plus seven. If you've ever done any addition in the past, I'm pretty confident you can solve this problem easily by adding two plus three, which will give you five than adding 5 to 7, which will give you an answer of 12. And that will give you the correct answer. And it's pretty easy because there are only three numbers. But as the column of numbers grows, solving the problem by adding the numbers from top to bottom can take quite a bit of time. So instead of adding the numbers vertically, let's try and spot the compliment, which were greatly reduced. Amount of time. It will take toe add numbers. So let's look at the problem again from the point of view where we're trying to spot compliments as we learn. Before, in our last video, we were exploring the concept of compliments of 10. We learned that three and seven is a complement of ton. That leaves us with one digit left, which is to, and we arrive at our final answer of 12 when we add two and turn. I know you may think that's basically the same as before when adding top to bottom. But I encourage you to keep watching this video and you'll see that as the numbers get bigger and the column gets longer, spotting compliments make solving the problem so much easier and faster. Far. Next problem. Let's take a look at nine plus one plus four. I know it's easy to spot the complement of 10 here, which is nine plus one. Then we have four love, which we easily add to 10 and that gives us a final answer of 14 for next problem. Let's take a look at two plus three plus eight. I'll give you a second toe, scanned the problem and try to spot the compliments. If you were unable to spot the complement of 10 it's OK. We'll be practicing a few more problems, and I'm sure you'll get the hang of it here. We can see that eight and two is a complement of ton which leaves us with three and we add the replace 10 which gives us a final answer of 13. You go start to see that spotting our compliments is faster than adding two plus three than adding eight for next problem. Let's make things a bit more challenging, so you can start to see the power of compliments. Let's add four plus five plus one plus six. I'll give you a quick second to pause the video and try to spot any compliments. Okay, lets see if we have any compliments by quickly scanning our problem here. I can see that four and six is a complement of 10. Then that leaves us with five and one, which we can quickly add up to six, and we finally add 10 and six, and that gives us a final answer off. 16 Far next problem. Let's take a look at a plus one plus two plus nine. I'll give you a second again to pause the video and try and spot any compliments. The first compliment I see by quickly scanning Our problem is a and to which is going to get us ton. That leaves us with one and nine which is another compliment of 10. And for our last step, we add 10 and 10 which gives us 20. Let's stop and think for a second how we would add these numbers, the tradition away from top to bottom. First, we would add a plus one, which would give us nine. Then we would add nine plus two, which would give us 11 and we would then add 11 plus nine and get our final answer was 20 which is more steps than training yourself to scanty problem. Look for compliments and at your compliments with the remaining numbers. I learned this trick years ago. I have never stopped using it. Of course, it takes practice and the morning trainer. I had a scanty problem. And spot your compliments, the quicker you'll be able to solve Single column addition. And in our next video, I'll show you how to add a double column. Addition. Problems quickly as well, which comes in handy even more than single column addition. But first, let's solve one more problem. Just to make sure you get the hang of spotting your compliments for our last problem, let's take a look at eight plus seven plus four plus three plus six. I'll give you a second to pause the video and try to spot any compliments. Were you able to spot any compliments of 10? The 1st 1? I was able to spot this seven and three, which gives us 10. A second compliment is four and six, which also gives us 10. And since we already know we have a compliment with seven and three, we know we have 20 so far, and that leaves us with one digit left eight, which, when we add to 20 gives us a final answer off. 28. Great. I hope with the problems we explored in this video, you were able to see how scanning your problems looking for compliments can help you solve addition problems much quicker and easier. I want to thank you for watching this video in our next video. We're going to learn how to add double digit numbers in a long column the same way as we learned that this video I look forward to seeing you there 4. Quickly Add Double Digit Numbers: Hey, everyone, welcome back. In our last video, we learned about quickly adding single column problems by spotting our compliments, which greatly reduces the amount of time it takes to add numbers. In this video, we will be learning about how to add double digit column problems with a mental math trick . I learned years ago I would love to share with you because even though I benefited from it while a school solving endless number of problems, when we think about it, Mathis something we have to deal with, whether or a school or not, because numbers revolves around every aspect of life. So why no learned techniques that makes things we deal with throught our life easier, far First problem. Let's take a look at 19 plus 31 if you haven't experienced with addition, I'm pretty sure you can solve this problem easy by looking at the column on the right and adding nine plus one, which will give us 10. We write down the river below, carry the one and most likely you need a pencil and paper to solve the problem. This way, a better and faster way to solve this problem without a pencil and paper is by looking at the numbers on the left column, and that's how we will solve all our problems throughout this video is by starting on the left and moving towards the right and let me show you why and how. If we take a look at the number 19 when we break this number down, the number one represents 10 because it's in the 10th place and the number nine is in the ones place, so it's simply nine. When added together, we have 19 Seimas. When we look at the number 31 the three represents 30 because it's in the 10th place and one is simply one because it's in the ones place. And when added together, we have 31 now, let's add. Since we know what every single digit and the problem represents, let's go back to the left column and add 10 plus 30 which is going to give us 40. And let's put that to the side because we still have more numbers to add. Next, we moved to the right column and add nine plus 40 which is going to give us 49 and for a last step, we add 1 to 49 that gives us a final answer of 50 before we move on to our next problem. Let's take a second look at the breakdown of our whole numbers and make sure our addition is right. 10 plus 30. It's going to give us 40 and nine plus one, gives us 10 and then we add 40 plus 10 and that gives us 50 Great. I know that's quite a few steps if this is your first time seeing this trick. But I can assure you, from years of adding double digit numbers like this, it's much faster than writing them down. And you'll see as the numbers get bigger for next problem. Let's take a look at another easy problem. Just when you can get the hang of the steps of quickly adding double digit column problems , Let's add 44 plus 68 just as we did before. We want to start on the left column and work our way towards the right. We can see we have four as six, which really means 40 as 60 because remember when we broke down our numbers in the last problem, we said the column on the left is in the 10th place. So four is 40 and 6 60 and when we add 40 and 60 that gives us 100. We put that to the side because we're adding in our head and we know we have a few numbers left. Next we move towards the right and remember, our numbers in the right column are in the ones place. So they are single digit numbers as opposed to the numbers on the Left column, which are in the 10th place and have a zero attached, making it a double digit number. So let's add 4 to 100 which is going to give us 104 And for our last step, we add eight toe 104 which is going to give us a final answer off 1 12 Great for next problem. Let's make things slightly more difficult by adding more digits, and I can assure you, as we make the problems longer, you'll start to see that adding this way, your mind makes adding a much faster than the traditional way for a final problem. Let's take a look at 1 12 plus 23 plus 34 just says before we can start on the left column and move towards the right. First, let's add 10 plus 20 which is going to give us 30. Next, we add 30 plus 30 which is going to give us 60. Next, we start to move towards the right. Call them where all our numbers are in the ones place. So let's add 2 to 60 which is going to give us 62. Next, we add 62 plus three, which is going to give us 65. And for a last step, we add our last number, which is four. And that's going to give us a final answer off 69. Great. I hope you're starting to see the power of adding numbers to sway in your mind. Of course, it takes practice, but I can assure you that as you practice more, you start to see how fast you can quickly add up numbers in your mind without the need of a pencil and paper. Far last problem. Let's add 39 plus 75 plus 63 plus 14. Let's start by adding just as we've been doing in our previous problems in the left column 30 plus 70 is going to give us 100. Let's put that to the side because we have a few more numbers to add to 100. Next, let's add 60 to 100 which is going to give us 1 60 Next, we add 10 to 1 60 that's going to give us 1 70 Next we add nine toe 1 70 that's going to give us 1 79 Next we add five toe 1 79 which is going to give us 1 84 Next we add 3 to 1 84 which is going to give us 1 87 and far last step. We add 4 to 1 87 which is going to give us 1 91 And that's our final answer. I hope with the examples on explanation I've given you helps you see how adding this way in your mind can make adding much faster. Of course, this is not something you'll be able to accomplish without practice, but I can assure you once you try over and over, you'll be amazed at the numbers you can add in your head. I want to thank you for watching this video. I really appreciate it. And I love being able to teach others know things. For next video will be exploring a topic which excites me even more than addition multiplication. We will be starting by learning how to quickly multiply two digits by one. I look forward to seeing you there. 5. Multiplying 2 digits by 1: Hey, everyone, welcome back in our last video we learned taught him mentally add double digit column problems. In this video, we will be learning how to multiply to to just buy one. I recommend he washed the previous video where we learned how to add a double digit numbers because it will help you understand some of the things will be learning in this video Far First problem. Let's multiply 14 times. Two. If you have any experience multiplying, I'm sure you can multiply this problem easily by multiplying two times for which would give us a then multiplying two terms, one which would give us to. And that would give us a final answer off 28 a faster way. You can multiply this problem, and any multiplication problem where you're multiplying to the spy one in your head is by reversing how we traditionally multiply instead of multiplying two times. For first, we can multiply two times one or in this case, 10 because one is in the 10th place and next we must apply to times four. And if you didn't watch the last video where we were adding double digit column problems, I'll quickly break down why one is really 10. So if we look at the number 14 the one is in the 10th place, which means has a zero attached to it, and four is in the ones place, so it's simply four. So let's try multiplying in our head. How I just discussed two times 10 is going to give us 20. We put that to the side because we're multiplying in our head and we have more numbers to multiply. Next we multiply two times four, which is going to give us a and we quickly add 20 plus eight, and we get our final answer off 28. I know that may seem like more steps, but I encourage you to keep watching and you'll see that as the numbers get bigger, multiplying this win your head, you'll be amazed at how fast you can arrive at the answer for next problem. Let's multiply 26 times three just says with it before we want to start multiplying on the left column and move towards the right. So three times 20 is going to give us 60. We put that to the side and continue multiplying three times six is going to give us 18. Next we add 60 plus 18 which is going to get us 78. And if you watched our last video where we learned how to quickly add double digit column problems, I'm sure you can quickly add that in your head after some practice. Far next problem. Let's multiply 43 times. Five. First, let's multiply five times 40 and it's 40 because our four is in the 10th place and that's going to give us 200. Next we multiply five times three is going to give us 15 and for our last step, we add 200 plus 15 which is going to give us to 15. Great. I hope you're starting to see how multiplying this way in your mind can really help speed things up. And in our next video, where we will be multiplying two digits by two digits, you see the power of being able to multiply this way in your head. But first list of one more problem just to get the hang of steps for next problem. Listen will supply 57 times seven. First we multiply seven times 50 which is going to give us 350. We put that to the side and next we multiply seven times seven, which is going to give us 49. And for our last step was simply add 3 50 plus 49 which is going to give us a final answer of 399. Great. This is going to conclude this video on multiplying two digits by one. In our next video, we will learn how to multiply two digits by two digits. I want to thank you for watching and look forward to seeing you there. 6. Multiplying 2 digits by 2: Hey, welcome back In our last video, we learned how to multiply two digits by one. In this video, we're going to advance things a bit and learned how to multiply two digits by two digits. This is a mental math trick where you'll really start to see the power of mental math. Shortcuts far. First problem. Let's multiply 23 times 12 First, I want to quickly show you the way we would normally solve this problem. Then I want to show you an amazing short cut that will help you solve this problem much faster. If you have any experience multiplying, I'm pretty sure you can multiply this problem by first multiplying two times three, which is going to give us six. Next we multiply two times two, which is going to give us four. We add our zero as a placeholder, and now we multiply by one. One times three is going to give us three. Next we multiply one times two, which is going to give us too. And for a final step, we add six plus zero is going to get us six four plus three is going to give us seven. Finally, we have two left, so we simply bring it down. Now, let me show you a quick away. You can solve this problem. And with enough practice, you wouldn't even need a pencil and paper to solve similar problems in the future. First, I want to place this indicator on the top left corner to help you see what stuff we're currently on. It's also show you that solving these problems on Lee requires three simple steps. Our first step is the same as we would normally multiply from the right vertically. So three times to is going to give us six far second step. We multiply across twice in an X, and after we multiply across, we add the two numbers, which result from the multiplying across. So, for example, two times two is four and three times one This three we add for which resulted from multiplying two times toe across, and we add three, which resulted from multiplying one times three across, and that's going to give us seven for our last up we multiply vertically again, but this time from the left times, one is going to give us, too. And we have our final answer. 276. I know that might be a bit confusing if it's your first time seeing this trick, but I can assure you, after solving a few more problems, you'll love multiplying this way because with enough practice, you can solve any two digit multiplication problem by just looking at it. So let's try another one for next problem. Let's multiply 31 times 41. Just as before, we start on the right side, multiplying vertically. One times one is going to give us one for a second step. We multiply across, and after we multiply across in an X, we added the result from multiplying across. So one times three is going to give us three and four times one is going to give us four. When we add three and four, that gives a seven. We write that down and move on to our next step for last step. We multiply three times for which is going to give us 12 and that gives us a final answer of 1271. Great. I hope you started to see that this technique allows you to solve problems faster, therefore allowing you to solve more problems in a shorter period of time. On a recommended do is practise and practise solving more problems, even solving five problems a day. And you'll be amazed at how quickly your mind starts to come up with the ants or faster for next problem. Let's take a look at 10 times 48 for first that let's multiply vertically from the right side. Eight times zero is going to give us zero. Next we multiply across in an X and add the results eight times. One is going to give us eight and four times zero is going to give us zero. So our answer is eight, because is there a plus? Eight is eight Next and far less step we will supply vertically from the left four times. One is going to give us four, and we have Our final ads are 480 great for next problem. We're going to look at a problem that's slightly different, and at extent you're probably wondering what happens when we have to carry a number. Let me show you for next problem. Let's take a look at 25 times. 17 far First up, let's do as we did before I multiply from the right vertically. Five times seven is going to give us 35. We write down the five and carry the three. But we are in carrying the three how we would traditionally carry it when we add or multiply, we're just putting it to the side and telling ourselves We need to add this to the result off our next step, which is multiplying across in an ex. Let me show you what I mean. For next step we multiply across in an X two times seven is going to give us 14 and one times five is going to give us five. And now we add 14 plus five plus two. Three, which we carried over is going to give us 22. We write down the to and carry the other to how we did our three, and we move on to our last step, where we multiply vertically from the left. Two times one is going to give us two plus that So we carried over is four and we have our final answer. 425. I know that may have been a bit confusing, but don't worry. Let's try similar problem so you can get the hang of the steps for next problem. Let's take a look at 68 times 49 just as we've been doing before, our first step is going to be multiplying from the right vertically. Eight times nine is going to give us 72. We're right down the to and carry the seven, which we add after we complete our second step, which is multiplying across. So let's multiply across six times nine is going to give us 54 and four times eight is going to give us 32. Now, we add, we know that 50 plus 30 is 80 and four plus two a six. So the result of multiplying across is 86 plus the seven we carried from where last step is going to give us 93. We're right down the three and we carry the nine and move on to our last step where we multiply vertically again. But this time from the left, six times four is going to give us 24 plus nine, which we carry from our last step is going to give us 33 and we have our final answer, which is 3332. Great. I hope you were able to see the benefits of using this mental math trick to quickly multiply two digit numbers. It does take some practice to multiply this way with holiday pencil on paper, but with enough practice, you'll be amazed at what you can do. And even if you do use a pencil on paper, this trick does allow you to multiply much faster, allowing you to solve more problems in a shorter period of time. This is going to conclude this video on multiplying two digit problems. In her next video, we will be learning one of my favorite math secrets, multiplying any number by 11 what you love to utilize when doing math your everyday life. I want to thank you for watching this video, and I look forward to seeing you in the next one 7. Multiply Any Number by 11: Hey, welcome back. In our last video, we learned how to multiply two digits by two digits. In this video, we're gonna be learning how to multiply 23 digit numbers by 11. If you haven't experienced multiplying and know your times table, you know that any number before 10 like 123 all the way up to nine is doubled when multiplied by 11. And as the numbers get bigger, it becomes more challenging to multiply by 11. So I want to teach you how you can quickly multiply any number by 11 without the need of a pencil and paper. For example, let's take a look at 16 times 11. This is a number that if we multiply, we would definitely need a pencil and paper because it requires quite a few steps. But I'll show you a quick shortcut word. You can solve any problem similar to this by just looking at it. The first thing we want to do when multiplying a two digit number by 11 is we want toe. Look at the number we're multiplying, which in this case is 16. We simply break the number up into single digit numbers, which becomes one and six and we add them. One plus six is going to give a seven. We placed at seven in the middle under the line, aware we wouldn't normally write our answer. One multiplying for last step. We put the first digit from the number. We're multiplying one in front of the seven like so and then we place the second digit in the number. We're multiplying six on the end like this and that's it. We're done. We just multiplied by 11 and we didn't even multiply. We basically added and then placed the first digit. We're multiplying in front and the second digit last. After we get the result from Addy, let's try a few more problems because that's how you become great. I using this mental math trick is by practicing for next problem. Let's multiply 23 times 11 same as before. We separate the number. We're multiplying by 11 in this case 23 which will simply give us two and three. We add them, which is going to give us five. We police that five in the middle and far last step. We simply bring down the first digit which were multiplying in this case two from 23 in front of the five, and then we simply bring down the second digit and place it after the five, and we have our final answer. 253. Let's try another problem for next problem less multiply 53 times 11. Now that we know what to do with the number we're multiplying by 11. Weaken. Simply add them in our mind because this is a mental math trick after all. So we know that five plus three is eight. We police that in the middle, and now we place our five on the left, and then we place our three on the right and we have our final answer. 583. And that takes as long as it takes us to add five plus three. Let's try one more problem just like this before I show you what happens when you most applying number in this fashion but have to carry a number when adding for next problem. Let's take a look at 72 times 11. Just as before, we simply add seven plus two because that's the number. We're multiplying by 11 and we know seven plus two is going to give us nine. Then we place our seven on the left and far final step. We place our two at the end on the right and we have our final answer off. 792. Great. I hope you're starting to see how multiplying by 11 with this mental math trick can greatly speed up the rate at which you can solve problems where you're multiplying by 11. But what happens when we have to carry a number? After adding, Let's see for next problem, let's take a look at 93 times 11 as we did before, let's break down. The numbers were multiplying 93 which is going to become nine and three. When we add nine plus three, that's going to give us 12. We place that 12 on the line where we would normally place our answer. Then we do as we did before we bring down the nine on the left and the three on the right and we have 9123. But we know that nine times 10 is 900 so we know that 9000 is the wrong answer. So What do we do on? We have four numbers. We add the first digit from the result of adding with the first digit of our answer. Remember when we added nine plus three? We got 12. So the first digit of 12 is one, and we simply add that with the first digit in our answer, which is nine, and that's going to give us 10 and we have our final answer. 1023. I know that might be become fusing due to the added steps, but let's try a few more and you'll see how easiest Selous to multiply any number by 11 with this mental math trick for next problem, let's multiply 78 times 11. The first thing we want to do is break down and add. The number were multiplying, so seven plus eight is going to give us 15. We placed a number under the line and we proceed to bring down our numbers on each side. So we place seven on the left and a at the end on the right. We know that 70 times 10 A 700 so we know that 7158 is too big. So we do as we did before. We add seven and one, and that's going to give us eight and we have our final answer. 858 for next problem. Let's add one more digit to the number where multiplying, let's multiply 324. First thing we want to do is break down the number we're multiplying, as we did in previous problems, but this time we're going to do it a bit differently. When we add this time, we're going to do it in pairs. For example, we will first ad three plus two, which is going to give us five. Next, we will add two plus four, which is going to get us six. Then we combined these two numbers on the line. We don't add them. We just place them together under the line, which is going to give us 56. Next, we bring down our numbers, as we did before on each side, and we have our final answer. 3564. Great. Let's try one more problem like this so you can get the hang of multiplying any number by 11 because At the end of the day, it doesn't matter how hard a problem is. It's all about knowing the steps to solve the problem. Once you know the steps to solve a problem, whether it's basic addition or a calculus, breaking down the steps makes it so much easier to solve the problem. Far Last problem. Let's multiply 538 times. 11 far First step we do as we did before. Add in pairs. First, let's add five plus three, which is going to give us eight. Then we add three plus eight, which is going to give us 11. Now we combined the numbers we added, and that's going to give us 100 and 11 before we bring down. The numbers were multiplying as we did before, we add, because if we bring down 100 and 11 and then proceed to bring down our numbers like five and eight, as we always do at the end to get our final answer, that would give us 58,118 which is going to be too big. So we simply just add eight plus one, which is going to give us 91. And now we place our numbers under the line. And for a final step, we bring down our numbers on each side. So we bring down the five on the left and eight on the right, and we have our final answer. 5918. Great. I hope you were able to see how fast you can multiply any number by 11. With this technique, of course, it does require some practice, but I can assure you, once you get the hang of this technique, you'll be amazed at how fast you can multiply any number by 11 in your mind. I want to thank you for watching and I look forward to seeing you in our next video. Thanks.