Multiple choice

Pipe A can fill a tank in 6 hours. Pipe B can fill the same tank in 3 hours. How long will it take to fill the tank if both pipes are opened together?

  1. 7

  2. 4

  3. 2

  4. 12

  5. 23
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Pipe A rate = 1/6. Pipe B rate = 1/3. Combined rate = 1/6 + 2/6 = 3/6 = 1/2. Time = 1 / (1/2) = 2 hours.

AI explanation

Using the formula for combined work, pipe A fills 1/6 of the tank per hour and pipe B fills 1/3 per hour. Their combined hourly rate is 1/6 + 1/3 = 3/6, which is 1/2 of the tank per hour. The total time to complete the job is the reciprocal of the combined rate, so 2 hours.

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