A snail is climbing out of a well – Interview Puzzle

(Last Updated On: May 24, 2016)

Snail climbing out of a well – Mathematical interview puzzle – A snail is at the bottom of a 30 foot well. Every hour the snail is able to climb up 3 feet and then it slides back down 2 feet. How many hours does it take for the snail to get out of the well?

Solution: To solve snail climbing puzzle we need to focus on two points.

Point-1

Since, in 1 hour snail climbs 3 feet and slides down 2 feet. Hence, Snail is covering 3 feet – 2 feet = 1 feet every hour.A snail is climbing out of a well puzzle

 

Point-2

Once snail reached at the top it would not slide back.  So, the position from where it will reach the top in 1 hour would be 30 feet (depth of well) – 3 feet (up distance covered in 1 hr) = 27th feet. Means, snail will not slide down when it start climbing from 27th feet.

 

 

Hence, as a result

As every hour snail is able to climbs 1 feet, it will climb 27 feet in 27 hours.

And last 3 feet it will cover in 1 hour from 27th position.

Hence, time taken to get out of well is:  27 hour+ 1hour = 28 hours.

Answer = 28 hours.