document.write( "Question 921387: One pipe can fill a tank in 15 minutes. The tank can be drained by another pipe in 45 minutes. If both pipes are opened, how long will it take to fill the tank? \n" ); document.write( "

Algebra.Com's Answer #558973 by josmiceli(19441) $\"\"$ $\"About$

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Rate of filling:
\n" ); document.write( " $\"+1%2F15+\"$ tanks / min
\n" ); document.write( "Rate of draining:
\n" ); document.write( " $\"+1%2F45+\"$
\n" ); document.write( "-----------
\n" ); document.write( "Let $\"+t+\"$ = time in min to fill tank
\n" ); document.write( " $\"+1%2F15+-+1%2F45+=+1%2Ft+\"$
\n" ); document.write( "Multiply both sides by $\"+45t+\"$
\n" ); document.write( " $\"+3t+-+t+=+45+\"$
\n" ); document.write( " $\"+2t+=+45+\"$
\n" ); document.write( " $\"+t+=+22.5+\"$
\n" ); document.write( "It takes 22.5 min to fill tank
\n" ); document.write( "and
\n" ); document.write( " $\"+.5%2A60+=+30+\"$
\n" ); document.write( "It takes 22 min 30 sec to fill tank\r
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "

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