There’s a frog – / Twenty-eight days.
If you hang out with math geeks, certain puzzles recur. One of these involves a frog in a 30-foot deep well. Each day, the frog hops up three feet. Each night, the frog sleeps and slips down two feet. How many days until the frog escapes the well? By the time you hit college, you’ve heard this one several times. Just as there are several puzzles you’ve heard ... too many times. My friends and I had heard these puzzles too many times. So when someone said “There’s a frog,” we were quick to blurt out “Twenty-eight days!” And that became a shorthand for cutting short too-familiar math puzzles. “U2 wants to cross a dark bridge but only has one flashli – ” “Twenty-eight days!” Twenty-eight days is not the answer to the U2 puzzle. And yet, it can be the answer to all such puzzles.
– Larry H. (October 7, 2000)
Tags: brainteaser | frog | math | nerd | puzzle