document.write( "Question 285929: Filling a tank. A water tank has an inlet pipe and a drain pipe. A full tank can be emptied in 30 minutes if the drain is opened and an empty tank can be filled in 45 minutes with the inlet pipe opened. If both pipes are accidentally opened when the tank is full, then how long will it take to empty the tank?
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Algebra.Com's Answer #207335 by ptaylor(2198)\"\" \"About 
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Let x=amount of time for pool to empty if both pipes are open
\n" ); document.write( "Then with both pipes open the pool empties at the rate of 1/x pool per min\r
\n" ); document.write( "\n" ); document.write( "Drain pipe empties at the rate of 1/30 pool per min
\n" ); document.write( "Inlet pipe fills at the rate of 1/45 pool per min\r
\n" ); document.write( "\n" ); document.write( "With both pipes open, the pool empties at the rate of:
\n" ); document.write( "1/30-1/45 pool per min, so:
\n" ); document.write( "1/30 - 1/45=1/x multiply each term by 90x
\n" ); document.write( "3x-2x=90
\n" ); document.write( "x=90 min----- time for pool to empty if both pipes are open\r
\n" ); document.write( "\n" ); document.write( "CK
\n" ); document.write( "with inlet pipe open, in 90 min we get 2 pools of water
\n" ); document.write( "with drain pipe open, in 90 min we drain 3 pools of water
\n" ); document.write( "3 pools - 2 pools= 1 pool of water drained\r
\n" ); document.write( "\n" ); document.write( "Hope this helps---ptaylor \n" ); document.write( "
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