SOLUTION: a pipe can fill a tank in 12 hours and another can empty in 24 hours. if both the pipes are used, with the first pipe running for 2 hours and second pipe running for 1 hour, altern

Question 706228: a pipe can fill a tank in 12 hours and another can empty in 24 hours. if both the pipes are used, with the first pipe running for 2 hours and second pipe running for 1 hour, alternatively, starting with the first pipe, then how long will it take to fill the tank
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
In other words, every 3 hours, the 1st pipe fills for 2 hours
and the 2nd pipe empties for 1 hour.
Let = time in hours to fill the tank
will be the 1st pipe's time filling
will be the 2nd pipe's time emptying
-----------
( 1 tank ) / ( 12 hrs ), or is the 1st pipe's rate
( 1 tank ) / ( 24 hrs ) or is the 2nd pipe's rate
-----------
Note that (rate)x(time) = fraction of tank filled or emptied

This says ( fraction of tank filled ) - ( fraction emptied ) = ( 1 tank filled )
Divide both sides by

It will take 24 hrs to fill the tank

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