Multiple choice general knowledge math & puzzles

A snail is at the bottom of a 20 meters deep pit. Every day the snail climbs 5 meters upwards, but at night it slides 4 meters back downwards. How many days does it take before the snail reaches the top of the pit

  1. 19

  2. 16

  3. 15

  4. 12

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

The snail gains 1 meter net per 24-hour cycle (5 up, 4 down). After 15 days, it reaches 15 meters. On the 16th day, it climbs 5 meters to reach the 20-meter mark. Once it reaches the top, it does not slide back, so it takes 16 days.