First it jumps up 5 steps.

Then it jumps down 2 steps.

Then it jumps up 5 steps.

Then it jumps down 2 steps.

And so it repeats, until it reaches the top. If -"

"25 jumps!" said Mark. "I know this one! It's with a well!"

"... no, not that one. Suppose you see the frog on top of the 38th step, and you know it started on top of one of the first ten steps. Which of those steps could it have started from?"

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This is fairly easy to solve in reverse.

38 is the starting number

**Edited by TheChad, 02 January 2012 - 07:12 AM.**