document.write( "Question 924077: Two pipes A and B fill a circular pond in 56 hour and 42hour respectively while a third pipe C can empty it in 72 hour .if all pipes are opened then what time will it takes to fill the circular pound? \n" ); document.write( "

Algebra.Com's Answer #560581 by josmiceli(19441) $\"\"$ $\"About$

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Add their rates of filling, making the rate
\n" ); document.write( "of emptying negative
\n" ); document.write( "----------------------
\n" ); document.write( "Pipe A:
\n" ); document.write( "( 1 pond filled ) / 56 hrs
\n" ); document.write( "Pipe B:
\n" ); document.write( "( 1 pond filled ( / 42 hrs
\n" ); document.write( "Pipe C:
\n" ); document.write( "( 1 pond emptied ) / 72 hrs
\n" ); document.write( "--------------------------
\n" ); document.write( "Let $\"+t+\"$ = time in hrs to fill the pond
\n" ); document.write( " $\"+1%2F56+%2B+1%2F42+-+1%2F72+=+1%2Ft+\"$
\n" ); document.write( " $\"+1+%2F+%28+7%2A8%29+%2B+1%2F%286%2A7%29+-+1%2F%289%2A8%29+=+1%2Ft+\"$
\n" ); document.write( "Multiply both sides by $\"+6%2A7%2A8%2A9%2At+\"$
\n" ); document.write( " $\"+6%2A9%2At+%2B+8%2A9%2At+-+6%2A7%2At+=+6%2A7%2A8%2A9+\"$
\n" ); document.write( "Divide both sides by $\"+3+\"$
\n" ); document.write( " $\"+18t+%2B+24t+-+14t+=+1008+\"$
\n" ); document.write( " $\"+28t+=+1008+\"$
\n" ); document.write( " $\"+t+=+36+\"$
\n" ); document.write( "The pond will fill in 36 hrs
\n" ); document.write( "check:
\n" ); document.write( "I can use my calculator
\n" ); document.write( " $\"+1%2F56+%2B+1%2F42+-+1%2F72+=+1%2F36+\"$
\n" ); document.write( " $\"+.017857+%2B+.023809+-+.013888+=+.027777+\"$
\n" ); document.write( " $\"+.027778+=+.027777+\"$
\n" ); document.write( "close enough
\n" ); document.write( " \n" ); document.write( "

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