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Wrapping presents at a table

Did you ever have to wrap a basketball as a present?

To see how the surface area of a sphere is really 4πr2, find a ball to wrap (a basketball works well). Cut some wrapping paper to fit the ball.

Then you’ll need to measure the circumference of the ball. You could wrap a piece of string around the ball. Then unwrap it and measure it with a ruler. Or you could wrap a piece of wrapping paper around the ball, since you’ve already got the wrapping paper handy.

Then lay the wrapping paper out flat and measure it to see whether the length is about the circumference of the ball and the width is about the diameter of the ball (a little less than a third of the circumference).

The area of your wrapping paper won’t be exactly right, because of the extra you need to be able to tape it, but it should be pretty close.

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Bibliography and further reading about circles:


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