"A carnival worker is asked to paint the deck of a carousel. Because the center of the carousel is occupied by machinery, he can't measure its diameter or even its radius. The best he can do is to take the measurement shown in green, which is 42 feet.
He's explaining this apologetically when his supervisor stops him. 'That's all the information we need,' he says. 'That's enough to tell us how much paint to buy.'
What's the area of the ring around the center of the carousel?"
For the answer go here. I recommend seeing if you can solve it yourself first. READYSETGO.