Question 72965

Let x=time it takes to fill bathtub with both faucets on.

Now we know that:

The cold water faucet fills at the rate of 1/12 of the bathtub per minute
The hot water faucet fills at the rate of 1/15 of the bathtub per minute

With both on, they fill at the rate of 1/12+1/15 or 5/60+4/60=9/60 of the bathtub per minute

Now, clearly 60/60 would be a full bathtub

So the equation we want to solve is 

(9/60)x=60/60 Multiply both sides by 60 to get rid of fractions

9x=60  divide both sides by 9
x=6.67 minutes--------------------------both filling together


Hope this helps----ptaylor