SOLUTION: An inlet pipe can fill a tank in 15 minutes. A drain can empty the tank in 20 minutes. If the tank is empty, and both the pipe and drain are open, how long will it take before the

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Question 1115563: An inlet pipe can fill a tank in 15 minutes. A drain can empty the tank in 20 minutes. If the tank is empty, and both the pipe and drain are open, how long will it take before the tank overflows?
Found 3 solutions by juno, josgarithmetic, ikleyn:
Answer by juno(1)   (Show Source): You can put this solution on YOUR website!
1/15-1/20=1/x
5/300=1/x
hence x=6
Answer by josgarithmetic(39617)   (Show Source): You can put this solution on YOUR website!
Fill rate both pipes open,




This is 60 minutes or 1 hour to fill the tank.
Answer by ikleyn(52778)   (Show Source): You can put this solution on YOUR website!
.
The inlet pipe fills    of the tank volume per minute.


The drain pipe empties    of the tank volume per minute.


So, the net inflow to the tank is the positive difference   =  =  of the tank volume per minute.


It means that the tank will be filled in 60 minutes = 1 hour if both pipes are open.

Solved.

================
It is a typical and standard joint work problem.

There is a wide variety of similar solved joint-work problems with detailed explanations in this site.  See the lessons
    - Using Fractions to solve word problems on joint work
    - Solving more complicated word problems on joint work
    - Selected joint-work word problems from the archive


Read them and get be trained in solving joint-work problems.

Also,  you have this free of charge online textbook in ALGEBRA-I in this site
    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this textbook under the topic
"Rate of work and joint work problems"  of the section  "Word problems".


Save the link to this online textbook together with its description

Free of charge online textbook in ALGEBRA-I
https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson

to your archive and use it when it is needed.


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