# Answer to Riddle #62: Climbing Snail, 3 Steps Forward, 2 Steps Back

62. A snail is at the bottom of a 30 foot well. Every hour the snail is able to climb up 3 feet, then immediately slide back down 2 feet. How many hours does it take for the snail to get out of the well?

There's a whole raft of puzzles of this form, usually 3 steps forward, usually 2 steps back; It might be walking uphill in the snow, something like that, there's a tiny little catch, lets take a look:

Before reading the answer can I interest you in a clue?

The plan here is that you will slightly out smart yourself and having worked out that the net speed is +1 foot per hour you will just use common sense and say 30feet at 1 foot an hour is 30 hours...

The answer is actually

I'd like to build a list of examples of this specific type of puzzle, if you see one I'd appreciate an email or hit me up on twitter @nigelcoldwell.

The plan here is that you will slightly out smart yourself and having worked out that the net speed is +1 foot per hour you will just use common sense and say 30feet at 1 foot an hour is 30 hours...

The answer is actually

**28 hours**. Why? The logic is true, 1 foot an hour for, let's say, 27 hours/feet, then at the end of the 28th hour the snail climbs 3 feet (making 30 feet,) and reaches the top before, this time, not sliding back.## Assumptions

The wording on these types of puzzle is always very precise. Or at least includes specific phrases like '*immediately slide back down*' these are obviously physical nonsense but they do point to the answer. The the plan to my mind is to work out the obvious route up to a safe distance from the end, in this case 27 hours/feet then model the exact behaviour. ie that in the next hour it climbs 3 feet and is instantly at the top of the well. Usually this is considered to be out of the well. Read the wording carefully.I'd like to build a list of examples of this specific type of puzzle, if you see one I'd appreciate an email or hit me up on twitter @nigelcoldwell.

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