One pump can fill a tank with oil in 4 hours. A second pump can fill the same tank in 3 hours. If both pumps are used at the same time, how long will they take to fill the tank?

1 Answer
Nityananda · Tony B
Nov 19, 2016

1 5/7157hours

Explanation:

First pump can fill the tank in 4 hours. So, In 1 hour it ill fill 1/414th of the tank.

Same way second pump will fill in 1 hour = 1/313rd of the tank.

If both pumps are used at the same time, then in 1 hour they will fill

" "1/4 + 1/3=[3+4]/12=7/12 14+13=3+412=712th of the tank.

Therefore tank will be full = 1 -: 7/12 = 12/7 = 1 5/7" "1÷712=127=157 hours

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