document.write( "Question 696749: Three pipes can fill a pool in eight hours. A drain can empty the full pool in twelve hours. How many hours will it take to fill a quarter of the pool if the three pipes and the drain are open? \n" ); document.write( "

Algebra.Com's Answer #429273 by josmiceli(19441) $\"\"$ $\"About$

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It doesn't matter that there are 3 pipes. It only matters
\n" ); document.write( "that all 3 are open, and, by themselves, they fill
\n" ); document.write( "the pool in 8 hrs.
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\n" ); document.write( "Add the rate of filling and subtract the rate of draining
\n" ); document.write( "to get the rate of filling
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\n" ); document.write( "( 1 pool filled ) / ( 8 hrs ) - ( 1 pool drained ) / ( 12 hrs ) = ( 1/4 pool filled ) ( t hrs )
\n" ); document.write( " $\"+1%2F8+-+1%2F12+=+%281%2F4%29+%2F+t+\"$
\n" ); document.write( "Bring the $\"+4+\"$ down to the denominator
\n" ); document.write( " $\"+1%2F8+-+1%2F12+=+1+%2F%284t%29+\"$
\n" ); document.write( "Multiply both sides by $\"+24t+\"$
\n" ); document.write( " $\"+3t+-+2t+=+6+\"$
\n" ); document.write( " $\"+t+=+6+\"$
\n" ); document.write( "1/4 of the pool will be filled in 6 hrs\r
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