Question

which of the following is the surface area of the right cylinder below?

(picture) http://i.imgur.com/91mchCb.png

please give me the best answer.

Answer 1

2pir^2 + 2pirh

Answer 2

i don't have calculator ;)

Answer 3

You need to add the area of the top and bottom, which is essentially 2πr^2. Then you need the surface area of the side, which is the circumference * height. So in all, thats 2πr^2 + πdh. So your radius is 6 and your height is 15. For the first part, 2πr^2 means 2*π*6^2, which is 72π. Then you need πdh. Diameter is twice the radius, so that means diameter is 12. So with a height of 15, you had π*12*15, which is 180π. The addition of the two, 180π + 72π = 252π.