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Some Similarities Between the Balls Used in Sports

Look at a basketball, football or soccer ball and do the following calculation: Count the number of pieces of material used to make the ball (or the number of regions between the lines on the ball). Subtract from this the number of seams on the ball (or the number of edges of separating the regions). Then add the number of points where two or more seams come together. The simplest is a football where there are 4 regions, 4 seams and two points where the seams come together. So for a football you get 4-4+2=2.

  Getting Started
  1. What number to you get for the other types of balls (basketball and soccer ball)?
  2. Take a balloon and mark it into regions with a marker. How does the number of regions - number of edges + number of corners change as you divide the balloon into more and more regions? Can you explain the pattern?
  Going Deeper

Try the same proceedure with a sheet of paper (mark it into regions and compute the number of regions - number of edges + number of corners). Try it with a bagel or doughnut.

 

Communicated by G. Hall.

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