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Topic: Data Science.

Difficulty:Intermediate.

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Objective: A snail is at the bottom of a 30-foot well. Every hour the snail can climb up 3 feet and then it slides back down 2 feet. How many hours will it take for the snail to get out of the well?

Short Answer: 28 hours.

Full Solution

We are told that every 1 hour, the snail climbs 3 feet and slides down 2 feet.

Therefore, it covers a distance of 3 – 2 = 1 foot every hour.

Also, we should establish that when the snail reaches the top, it will not slide back.

So, the position from where it will reach the top in 1 hour would be:

30 feet – 3 feet (upward distance covered in 1 hr) = 27 feet.

This means that the snail will not slide down when it starts climbing from the 27th feet.

Since the snail climbs a total of 1 foot every hour, it will climb 27 feet in 27 hours, and the last 3 feet will be covered in 1 hour from 27th feet.

Hence, the time taken to climb to the top of the well is:
27 hours + 1 hour = 28 hours.