Question

Can somebody help me ?

Answer 1

The surface area formula is $A=2$π$rh+2$π$r^2$.

Using the formula, you can determine that the answer is C.

Answer 2

To find the surface area of a cylinder, you have to add the areas of the two bases and then find the area of the section that wraps around. There is a simple trick to finding the area of the wraparound section, but first we need the area of the base.


The base is circular so we know the area is pi times the radius squared:
$\pi$ r^2 = $\pi$ (36) so the two bases add together to make 2 times $\pi$ times 36.

Imagine you took just the wraparound piece and unraveled it, it would be in the shape of a rectangle. This means the height of the cylinder would be the height of the rectangle and the circumference of the base would be the length. Circumference is $\pi$ times the diameter, so the length of our "rectangle" would be $\pi$ times 12. To find the area we multiply this by our height to get: $\pi$ times 12 times 15.1 which equals our surface area.

Now we can plug the following into our calculator to get an answer:

2( $\pi$ 36) + 12 $\pi$ 15.1 = 795.45

Choice C is correct.