Since each hose makes the filling time less, we have to add the reciprocals together and take the reciprocal of the result.

We need to use:

`1/T=1/T_1+1/T_2`

So we have:

`1/T=1/7+1/10`

`1/T=(10+7)/70=17/70`

So

`T=70/17=4.1176`

So it will take 4.1 minutes to fill the tank with both hoses operating together.

Get the Daily Math Tweet!
IntMath on Twitter