Question

What is the surface area of a cylinder with a radius of 3 and a height of 7

Answer 1

The surface area of a cylinder includes the area of two circle bases as well as the tube connecting the bases.

Let's start with the circles. The area is pi*r^2.
pi*3^2 = 9pi

If we were to flatten a cylinder, this tube would actually be a rectangle with a length equal to the circumference of the circle. The circumference of a circle is 2pi*r.

So the rectangle has an area of 7*(2pi*3) = 42pi

There are two circular bases, so the surface area is:

2(9pi) + 42pi = 60pi
Or 60*3.14 = 188.4