Escaping Frog
A frog is at the bottom of a 30 meter well. Each day he summons enough energy for one 3 meter leap up the well. Exhausted, he then hangs there for the rest of the day. At night, while he is asleep, he slips 2 meters backwards. How many days does it take him to escape from the well?
Note: Assume after the first leap that his hind legs are exactly three meters up the well. His hind legs must clear the well for him to escape.
The answer is 28.
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Because each day leaps 3 meters up and slips 2 down for one day it will climb 1 meter. For 27 days it will climb 27 meters on the 28 day it will be out of the well.