document.write( "Question 489531: The fill pipe for a tank can fill the tank in 4 hours, and the drain pipe can drain it in 2 hours. If both pipes are accidentally opened, how long will it take to empty a half-filled tank? \n" ); document.write( "

Algebra.Com's Answer #333764 by ankor@dixie-net.com(22740) $\"\"$ $\"About$

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The fill pipe for a tank can fill the tank in 4 hours, and the drain pipe can drain it in 2 hours.
\n" ); document.write( "If both pipes are accidentally opened, how long will it take to empty a half-filled tank?
\n" ); document.write( ":
\n" ); document.write( "Let t = time to empty the tank with both valves open
\n" ); document.write( "Let an empty tank = 1
\n" ); document.write( "then a half empty tank = .5
\n" ); document.write( ":
\n" ); document.write( " $\"t%2F2\"$ - $\"t%2F4\"$ = .5
\n" ); document.write( "multiply 4, results:
\n" ); document.write( "2t - t = 4(.5)
\n" ); document.write( "t = 2 hrs to empty the tank \n" ); document.write( "

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