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Interview prep / Brainteaser/Logic

Climbing snail on a ten-foot post

Question

A snail sits at the foot of a post 1010 feet tall. Each day it climbs 33 feet, and each night it slides back 11 foot. On which day does it first reach the top?

Short answer

During day 5. Each full day-night cycle nets 22 feet, so the snail starts day 5 at 88 feet. That day's 33-foot climb takes it past 1010 feet before it can slip back (after about two-thirds of the day).

Adapted from Crack, Heard on the Street, Q1.24, p.14; question and answer rewritten by SelfMadeQuant.com.

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