Frog leaping 3m and slipping 2m

Problem:

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?

Solution:

Each day he makes it up another meter, and then on the twenty seventh day he can leap three meters and climb out. On the 28th day, he will leap and get out.

Answer:

                 28 Days