SOLUTION: Used by itself, the cold water faucet can fill a bathtub in 12 minutes. It takes 15 minutes for the hot water faucet to fill the bathtub. If both faucets are on, how long will it t

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Question 72965: Used by itself, the cold water faucet can fill a bathtub in 12 minutes. It takes 15 minutes for the hot water faucet to fill the bathtub. If both faucets are on, how long will it take to fill the bathtub?(round to the nearest .01 minute)
Answer by ptaylor(2198) About Me  (Show Source):
You can put this solution on YOUR website!

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