The red figure at the right is made of two hemispheres of equal radius. The blue cylinder at the left has the same radius and height as the red figure.
Which shape has a larger surface area?
The red figure will just have the surface area of a sphere of radius r
So....its surface area is 4pir^2
The height of the cylinder = 2r
So......its surface area is [ 2pi (r^2) + 2pi*r (2r) ] = [ 2pi(r^2) + 4pir^2 ]
So the cylinder has the greater surface area