A pipe can fill a tank in 10 h, while an another pipe can empty it in 6 h. Find the time taken to empty the tank, when both the pipes are opened up simultaneously.

A) 11 h

B) 15 h

C) 18 h

D) 16 h

Correct answer:
B) 15 h

Description for Correct answer:
Part filled by 1st pipe in 1 h = \( \Large \frac{1}{10} \)

Part emptied by 2nd pipe in 1 h = \( \Large \frac{1}{6} \)

Part emptied when both the pipes are opened up

= \( \Large \frac{1}{6} \) - \( \Large \frac{1}{10} \) = \( \Large \frac{5-3}{30} \)=\( \Large \frac{2}{30} \)=\( \Large \frac{1}{15} \)

Hence, time taken to empty the full tank in 15 h.


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