Question

20 COINS

Answer 1

The surface area of a cylinder is given by

$A_A = 2\pi rh$

which is the surface area of cylinder A.

To compute the surface area of cylinder B, we have to map $(r,h)\mapsto (2r, 2h)$ and we have the following formula

$A_B = 2\pi(2r)(2h)$

If we manipulate the second expression, we have

$A_B = 8\pi rh$

Which implies

$\dfrac{A_B}{A_A} = \dfrac{8\pi rh}{2\pi rh} = 4$