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The Loop

Pi Day: How long is "one more roll"?

March 14, 2015

When a ball stops on the rim of the cup, golfers and TV announcers often say that it needed "one more roll" or "one more rotation." But they're wrong, and Pi Day -- which celebrates the discovery of the mathematical ratio between a circle's diameter and its circumference, and is celebrated for obvious reasons today, on 3/14 -- is the ideal time to explain why. A golf ball, to be legal, has to be at least 1.68 inches in diameter. That means that its circumference -- the length of "one more roll" -- is at least 3.14 times 1.68, or 5.28 inches. And that length is eerily similar to one that was in the news earlier this month. Coincidence?