document.write( "Question 570697: one pump can drain a pool in 9 minutes. When a second pump is also used, the pool only takes 5 minutes to drain. How long would it take the second pump to drain the pool if only one pump is used? \n" ); document.write( "

Algebra.Com's Answer #367738 by josmiceli(19441) $\"\"$ $\"About$

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Let the time to drain the pool for 2nd pump = $\"t\"$
\n" ); document.write( "The 1st pump's rate of draining is $\"+1%2F9+\"$
\n" ); document.write( "which means ( 1 pool ) / ( 9 min )
\n" ); document.write( "The 2nd pump's rate of draining is $\"+1%2Ft+\"$
\n" ); document.write( "which means ( 1 pool ) / ( t minutes )
\n" ); document.write( "Together, their rate of draining is $\"+1%2F5+\"$
\n" ); document.write( "------------------------------
\n" ); document.write( "To find the rate when both are used, add their
\n" ); document.write( "individual rates
\n" ); document.write( " $\"+1%2F9+%2B+1%2Ft+=+1%2F5+\"$
\n" ); document.write( "Multiply both sides by $\"+45t+\"$
\n" ); document.write( " $\"+5t+%2B+45+=+9t+\"$
\n" ); document.write( " $\"+4t+=+45+\"$
\n" ); document.write( " $\"+t+=+11.25+\"$
\n" ); document.write( " $\"+.25%2A60+=+15+\"$
\n" ); document.write( "The 2nd pump can drain the pool in 11 min and 15 sec
\n" ); document.write( "operating alone \n" ); document.write( "

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