Brainteaser: A snail is at the bottom of a 10-foot well. Each day it climbs up 3 feet, and each night it slides back down 2. How many days until it gets out?
Answer: 8 days. It nets 1 foot every 24 hours, so the instinct is to say 10. But on the morning of day 8 the snail starts from 7 feet, climbs its 3 feet, and reaches the top at 10 feet. It’s already out, so there’s no night eight to slide back down.
