SOLUTION: One pipe can fill a tank in 20 minutes, while another takes 30 minutes to fill the same tank. How long would it take the two pipes together to fill the tank?

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Question 742195: One pipe can fill a tank in 20 minutes, while
another takes 30 minutes to fill the same tank. How long would it take the two pipes together to fill the tank?
Found 5 solutions by lynnlo, ikleyn, greenestamps, josgarithmetic, MathTherapy:
Answer by lynnlo(4176) About Me  (Show Source):
Answer by ikleyn(53570) About Me  (Show Source):
You can put this solution on YOUR website!
.
One pipe can fill a tank in 20 minutes, while another takes 30 minutes to fill the same tank.
How long would it take the two pipes together to fill the tank?
~~~~~~~~~~~~~~~~~~~~~~~~~ 

First  pipe fills 1/20 of the tank volume per minute when works alone.

Second pipe fills 1/30 of the tank volume per minute when works alone.


Working together, both pipes fill  

    1%2F20 + 1%2F30 = 3%2F60 + 2%2F60 = 5%2F60 = 1%2F12 

of the tank volume per minute.


Hence, it will take 12 minutes for both pipes to fill the tank.    ANSWER

Solved.

The answer in the post by @lynnlo is incorrect.



Answer by greenestamps(13292) About Me  (Show Source):
You can put this solution on YOUR website!


Here is a different way of solving a problem like this.

Consider the least common multiple of the two given times, which is 60 minutes.

In 60 minutes, the first pipe could fill the tank 60/20 = 3 times.
In 60 minutes, the second pipe could fill the tank 60/30 = 2 times.
So in 60 minutes together the two pipes could fill the tank 3+2 = 5 times.
So the time it takes the two pipes to fill the tank one time is 60/5 = 12 minutes.

ANSWER: 12 minutes

NOTE: Both this method and the method shown by the other tutor can be used to solve similar problems in which one pipe is trying to fill the tank while another pipe is trying to drain the tank.

Answer by josgarithmetic(39720) About Me  (Show Source):
You can put this solution on YOUR website!
                   RATE          TIME        TANKS

ONE PIPE             1/20           20         1

ANOTHER PIPE         1/30           30         1

If the two pipes are used together for filling the one tank, then
%281%2F20%2B1%2F30%29%2Ax=1

%283%2B2%29x=60

5x=60

x=12---------------twelve minutes

Answer by MathTherapy(10704) About Me  (Show Source):
You can put this solution on YOUR website!
One pipe can fill a tank in 20 minutes, while	
another takes 30 minutes to fill the same tank. How long would it take the two pipes together to fill the tank?

Answer is RIGHT HERE, below.....Question 45662:
Hi again,
I need some assistance with this mixture problem:
It takes a pipe 10 minutes less than another one to fill a tank of water. Both pipes together can fill the tank
in 12 minutes. How long will it take each one to fill the tank separately?
I am having trouble on how to start setting the equation up.
Thanks again,
Lou