document.write( "Question 498554: Pipe A can fill a pool in 5 hours. Pipe B can fill it in 2 hours less than it takes Pipe C, a drain pipe, to empty the pool. With all 3 pipes open it takes 3 hours to fill the pool. How long would it take Pipe C to empty it? \n" ); document.write( "
Algebra.Com's Answer #337070 by josmiceli(19441)\"\" \"About 
You can put this solution on YOUR website!
This is a problem of rates
\n" ); document.write( "Let \"c\" = pipe C's rate of emptying the pool
\n" ); document.write( "Pipe A's rate of filling:
\n" ); document.write( "\"+1%2F5+\" ( 1 pool in 5 hrs )
\n" ); document.write( "Pipe B's rate of filling:
\n" ); document.write( "\"++1%2F%28+c+-+2%29+\"
\n" ); document.write( "Pipe C's rate of emptying pool:
\n" ); document.write( "\"c\"
\n" ); document.write( "----------
\n" ); document.write( "With all 3 pipes open:
\n" ); document.write( "\"+1%2F5+%2B+1%2F%28+c+-+2+%29+-+1%2Fc+=+1%2F3+\"
\n" ); document.write( "Multiply both sides by \"+15%2Ac%2A%28+c+-+2+%29+\"
\n" ); document.write( "\"+3c%2A%28+c+-+2+%29+%2B+15c+-+15%2A%28+c+-+2+%29+=+5c%2A%28+c+-+2+%29+\"
\n" ); document.write( "\"+3c%5E2+-+6c+%2B+15c+-+15c+%2B+30++=+5c%5E2+-+10c+\"
\n" ); document.write( "\"+2c%5E2+-+4c+-+30+=+0+\"
\n" ); document.write( "\"+c%5E2+-+2c+-+15+=+0+\"
\n" ); document.write( "Completing the square:
\n" ); document.write( "\"+c%5E2+-+2c+%2B+%28-2%2F2%29%5E2+=+15+%2B+%28-2%2F2%29%5E2+\"
\n" ); document.write( "\"+c%5E2+-+2c+%2B+1+=+16+\"
\n" ); document.write( "\"+%28+c+-+1+%29%5E2+=+4%5E2+\"
\n" ); document.write( "Take the square root of both sides
\n" ); document.write( "\"+c+-+1+=+4+\"
\n" ); document.write( "\"+c+=+5+\"
\n" ); document.write( "and, also
\n" ); document.write( "\"+c+-+1+=+-4+\"
\n" ); document.write( "\"+c+=+-3+\" ( can't use the negative square root )
\n" ); document.write( "It will take pipe C alone 5 hours to empty pool
\n" ); document.write( "check answer:
\n" ); document.write( "\"+1%2F5+%2B+1%2F%28+c+-+2+%29+-+1%2Fc+=+1%2F3+\"
\n" ); document.write( "\"+1%2F5+%2B+1%2F%28+5+-+2+%29+-+1%2F5+=+1%2F3+\"
\n" ); document.write( "\"+1%2F5+%2B+1%2F3+-+1%2F5+=+1%2F3+\"
\n" ); document.write( "\"+1%2F3+=+1%2F3+\"
\n" ); document.write( "OK\r
\n" ); document.write( "\n" ); document.write( "
\n" ); document.write( "
\n" );