Multiple choice

Pipes A, B and C are connected to an empty tank. While the first two pipes can fill the tank in 6.6 and 16.5 hours respectively, the third pipe can empty the tank in 9.9 hours after filling. If all the three pipes are opened simultaneously after filling the tank 3/5, then how many hours will it take to fill the tank?

  1. 3.5

  2. 3.6

  3. 3.75

  4. 4
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Combined rate = 1/6.6 + 1/16.5 - 1/9.9 = 15/99 + 6/99 - 10/99 = 11/99 = 1/9 tank/hr. Tank is 3/5 full, so 2/5 remains. Time = (2/5) ÷ (1/9) = 18/5 = 3.6 hours.

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