Question

Tap A can fill a tank in 5 minutes. Tap B can fill the same tank in 8 minutes, Tap C can empty the same tank in 10 minutes. If all taps are opened at the same time, how long does it take to fill the tank?

Answer 1

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Tap A fills 1/5 part

Tap B fills 1/8 part

Tap A + Tap B fills in = 1/5 + 1/8 = 13/40 part

Tap C empty the tank in 1/10 part

Time taken to fill the tank = 13/40 - 1/10 = 9/40 = 40 minutes 9 seconds.