Multiple choice general knowledge math & puzzles

A tap can fill the tank in 16 minutes and another can empty it in 8 minutes. If the tank is already half full and both the taps are opened together, the tank will be:

  1. filled in 12 min

  2. emptied in 12 min

  3. filled in 8 min

  4. emptied in 8 min

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

Fill tap rate: 1/16 tank per minute. Empty tap rate: 1/8 tank per minute. Net rate when both open: 1/16 - 1/8 = 1/16 - 2/16 = -1/16 tank per minute (negative means emptying). Tank is half full (1/2). Time to empty: (1/2) ÷ (1/16) = (1/2) × 16 = 8 minutes.