Multiple choice

Pipe A can fill a tank in 10 hours and Pipe B can fill the same tank in 12 hours. Both the pipes are opened to fill the tank and after 3 hours pipe A is closed. Pipe B will fill the remaining part of the tank in

  1. 5 hr

  2. 4 hr

  3. 5 hr 24 min

  4. 3 hr
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Pipe A fills 1/10 of tank per hour, Pipe B fills 1/12 per hour. Together they fill 1/10 + 1/12 = 11/60 per hour. In 3 hours, they fill 33/60 = 11/20 of tank. Remaining = 9/20 of tank. Pipe B alone needs (9/20) / (1/12) = 9/20 × 12 = 108/20 = 5.4 hours = 5 hours 24 minutes. Option C is correct.

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