document.write( "Question 245699: A water tank can be filled in 7 minutes and emptied in 9 minutes. If the drain is accidentally left open when the tank is being filled, how long does it take to fill the tank? \n" ); document.write( "

Algebra.Com's Answer #179416 by stanbon(75887) $\"\"$ $\"About$

You can put this solution on YOUR website!
A water tank can be filled in 7 minutes and emptied in 9 minutes. If the drain is accidentally left open when the tank is being filled, how long does it take to fill the tank?
\n" ); document.write( "----------------------
\n" ); document.write( "Filling rate = 1/7 tank/min
\n" ); document.write( "----
\n" ); document.write( "Emptying rate = 1/9 tank/min
\n" ); document.write( "--------------------
\n" ); document.write( "Let the time to fill the tank be \"x\".
\n" ); document.write( "Together rate = 1/x tank/min
\n" ); document.write( "---------------------------------------------
\n" ); document.write( "Equation:
\n" ); document.write( "rate - rate = together rate
\n" ); document.write( "1/7 - 1/9 = 1/x
\n" ); document.write( "---
\n" ); document.write( "9x - 7x = 7*9
\n" ); document.write( "2x = 63
\n" ); document.write( "x = 31.5 hrs (# of hrs. required to fill the tank)
\n" ); document.write( "======================================================
\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H. \n" ); document.write( "

\n" );