Father and child take a sheet of newspaper and cut off a two-inch strip about three inches long. Give the strip a half twist, overlap the ends, and paste them together to make a circle. Cut the strip down the center lengthwise. You should get two circles, shouldn't you? But look! You have one circle twice as large as your first circle. Now cut this strip down the center, lengthwise. Will you get another circle twice as big as the one you were cutting? No, you have two pieces linked together like a chain.