Multiple choice

Pipes A and B can fill a tank separately in 36 and 48 hours respectively. Both pipes are opened together to fill the tank. After some time pipe B is closed and the tank is full in 24 hours. How much time was the pipe B open?

  1. 12 hours

  2. 14 hours

  3. 16 hours

  4. 18 hours
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Pipe A fills at 1/36 per hour and B at 1/48 per hour. If B is open for t hours, total filled = t/48 + 24/36 = 1. Solving: t/48 = 1 - 2/3 = 1/3, so t = 16 hours. Option C is correct.

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