Multiple choice general knowledge math & puzzles

A monkey starts climbing up a tree 20ft. tall. Each hour, it hops 3ft. and slips back 2ft. How much time would it take the monkey to reach the top?

  1. 19 hours.

  2. 18 hours

  3. 16 hours

  4. 18.5 hours

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Each hour the monkey climbs 3ft and slips 2ft, gaining 1ft net. However, when it reaches the top, it doesn't slip back. After 17 hours it's at 17ft. In the 18th hour, it climbs 3ft to reach 20ft (the top) and is done - no slipping occurs at the top. The answer is 18 hours, not 20.