I have a geometry question..

Question

I am having trouble with this geometry word problem. If you could explain in detail it would be greatly appreciated.

 

In making a ( two-dimensional) net of a cylinder, Mark was confused. He thought that since the bases were circles that two of the edges of the lateral surface would be round. He wondered how it could be a rectangle. How would you help Mark visualize what the net should be?

 

Thank you so much in advance!

Answer 1

My favorite example is the cardboard of a tissue roll. If you make one cut along the height of the cylinder, you will make a rectangle.

 

I don't know though if the answer you need should be technical or something but that's the usual example I use for my students to understand the lateral surface area of a cylinder.

 

In a more technical approach, if you cut a cylinder along the height, the loop of the circumference of the base will be gone hence turning it into a line when spread out. When it is spread out, you could say that the circumference will be the width while the height of the cylinder will be the length of the rectangle.

 

And yes, I don't think the technical approach will help Mark faster than the tissue roll.