A snail climbs five inches up a vertical wall each day, but slips four inches down the wall each night. If it starts climbing on the beginning of the first day, on which day will it reach the top of a wall that is 30 inches high?

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mathematics

This classic brain teaser trips people up because it seems like a straightforward math problem. At first glance, you might calculate the snail's net progress. It climbs five inches and slips four, resulting in a net gain of one inch per 24-hour cycle. Following this logic, it would seem to take 30 days to climb a 30-inch wall. However, this overlooks one crucial detail about the snail’s final push to the top.

The key to solving this puzzle is to realize that once the snail reaches the summit, its journey is over;

A snail climbs five inches up a vertical wall each day, but slips four inches down the wall each night. If it starts climbing on the beginning of the first day, on which day will it reach the top of a wall that is 30 inches high?

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