Understanding Volumes in space

Understanding Volumes in space - student project

I found cutting the shapes actually quite therapeutic! 

 

I had some difficulty cutting the spheres- for example, in the first sphere on the left, i can tell I need to add anouther line if  it is a 'true quarter cut', but I do not know how to properly construct the line that would dissect the sphere in the right spot. 

Understanding Volumes in space - image 1 - student projectUnderstanding Volumes in space - image 2 - student project

Understanding Volumes in space - image 3 - student projectUnderstanding Volumes in space - image 4 - student project

Feels like my cylinders don't always look right even with the principles for some reason!

 

I freehanded the boxes (not the construction lines). 
Understanding Volumes in space - image 5 - student project

Understanding Volumes in space - image 6 - student projectUnderstanding Volumes in space - image 7 - student projectUnderstanding Volumes in space - image 8 - student projectUnderstanding Volumes in space - image 9 - student project