Question

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?

Answer 1

`1 5/7`hours

Explanation:

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

Same way second pump will fill in 1 hour = `1/3`rd 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`th of the tank.

Therefore tank will be full = `1 -: 7/12 = 12/7 = 1 5/7" "`hours