Tennis Ball Container

In this puzzle we ask you to make a usable label for a tennis ball container.

You have a cylindrical container just big enough to hold three tennis balls. Now you want to make a label for the container, and you have to decide whether to wrap the label around the cylinder or up the side. Which direction is longer?

Make up some puzzles like these and send them in with your solutions. We will post them in the SEED Science Center.

Course:

Math [1]

Result/Solution(s)

The wrap-around distance is a bit longer than the end-to-end distance. Here's why:

The balls "just fit" in the tube, and let's assume that the walls and ends of the container are very thin, so for purposes of calculations we can ignore their thickness.

The length of the container is three times the diameter of a tennis ball. The distance around the container is the distance around one of the balls at its fattest point. This is equal to pi times the diameter of a ball.

Pi is equal to 3.1416. Since this is more than 3, the distance around the container is more than the end-to-end distance.

Pi is a special number that is defined as the ratio of the circumference of a circle to its diameter. This is true of all circles. Calculations of pi have become more accurate over the years. Thousands of years ago it was thought to be 3.

3.1416 is actually an approximation. Pi is a non-repeating decimal number that will go on forever. If you calculate it to ten digits, it is equal to 3.141592653.

Here are other Web sites with information about pi:

www-gap.dcs.st-and.ac.uk/~history/HistTopics/Pi_through_the_ages.html [2]

Math Puzzle [3]