Question

A square with an area of 81 cm^2 is rotated to form a cylinder. What is the height of the cylinder?

Answer 1

The area of a square is just:

A=s^2 so

s^2=81

s=9  so if this square is rotated about its center you will get a cylinder with a radius of 4.5 cm and a height of 9 cm.

So the height is 9 cm