SOLUTION: Hi The problem: A large water tank has two inlet pipes of different sizes and one outlet pipe. With the outlet pipe closed it takes 3 hours to fill the empty using the la

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Question 628805: Hi
The problem:
A large water tank has two inlet pipes of different sizes and one outlet pipe.
With the outlet pipe closed it takes 3 hours to fill the empty using the large inlet pipe only. It takes 4 hours to fill the empty tank using the small inlet pipe only.
When the tank is full and the inlet pipes are closed it takes the outlet pipe 8 hours to empty the tank.
Assuming the tank is empty and all three pipes are opened how long will it take to fill the tank to the nearest minute.
Thankyou

Answer by nerdybill(7384) About Me  (Show Source):
You can put this solution on YOUR website!
A large water tank has two inlet pipes of different sizes and one outlet pipe.
With the outlet pipe closed it takes 3 hours to fill the empty using the large inlet pipe only. It takes 4 hours to fill the empty tank using the small inlet pipe only.
When the tank is full and the inlet pipes are closed it takes the outlet pipe 8 hours to empty the tank.
Assuming the tank is empty and all three pipes are opened how long will it take to fill the tank to the nearest minute.
.
Let x = time (hours) it takes to fill tank
then
x(1/3 + 1/4 - 1/8) = 1
multiplying both sides by 24:
x(8 + 6 - 3) = 24
x(14 - 3) = 24
x(11) = 24
x = 24/11 hours
or
x = 2 hours and 11 minutes