SOLUTION: Pipe A can fill a tank in 4 hours and pipe B can fill the tank in 1/2 the time required for pipe C to empty the tank. When all three pipes are open the tank is filled in 2.4 hours.

Question 920224: Pipe A can fill a tank in 4 hours and pipe B can fill the tank in 1/2 the time required for pipe C to empty the tank. When all three pipes are open the tank is filled in 2.4 hours. How long for C to drain the tank?
I tried setting up a table. But I'm not sure what the significance of whether the tank is being filled or emptied is.
Thank you for helping.

Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Rates of FILLING are (+)
Rates of emptying are (-)
-----------------------
Rate of filling for pipe A:
( 1 tank ) / ( 4 hrs )
------------------------
Let = rate of emptying for pipe C
= rate of filling for pipe B
( 1/2 the time means twice the rate )
------------------------------------
Add the rates with all 3 pipes open:

Multiply both sides by

---------------

In minutes:

Pipe C drains the tank in 10 min
------------------------------
check:

Multiply both sides by

OK
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