Question

You have a coin bank in the shape of a cylinder. It has a radius of 1.5 inches and a height of 5 inches. What is the surface area of the coin bank? Use 3.14 to approximate pi. Round to the nearest hundredth.

Answer 1

The surface area of a cylinder consists of the two circles on either end, and the curved area around the middle. The circles have radii of 1.5 inches, so an area of pi*r^2 = 3.14 * 1.5^2 = 7.065 square inches. The curved area can be thought of as a rectangle, like a label wrapping round the cylinder. The length of the rectangle is 5 inches, and the width of the rectangle is the circumference of one of the circles, 2*pi*r = 2 * 3.14 * 1.5 = 9.42 inches. The area of the rectangle is 9.42 * 5 = 47.1 square inches. Putting all that together, the surface area is 7.065 + 7.065 + 47.1 = 61.23 square inches.