document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1200985>Question 1200985</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A water tank can be filled by an inlet pipe in  <BR>\n" );
document.write( "9<BR>\n" );
document.write( "  hours. It takes  <BR>\n" );
document.write( "4<BR>\n" );
document.write( "  times as long for the outlet pipe to empty the tank. How long will it take to fill the tank if both pipes are open? </SPAN>\n" );
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document.write( "The tank can be completely filled in 9 hours.\r<BR>\n" );
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document.write( "It takes 4 times as long to empty the tank. <BR>\n" );
document.write( "It takes 4*9 = 36 hours to empty the tank.\r<BR>\n" );
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document.write( "Let's say the tank was 36 gallons.\r<BR>\n" );
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document.write( "The fill rate is 36/9 = 4 gallons per hour.<BR>\n" );
document.write( "Formula:<BR>\n" );
document.write( "rate = (amount done)/(time)\r<BR>\n" );
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document.write( "The drain rate would be 36/36 = 1 gallon per hour.\r<BR>\n" );
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document.write( "Subtract those two rates<BR>\n" );
document.write( "4-1 = 3<BR>\n" );
document.write( "This indicates the net rate is +3 gallons per hour. <BR>\n" );
document.write( "The plus or positive means more water enters the tank than is drained. <BR>\n" );
document.write( "Overall, the tank is getting filled up even if the drain pipe is open.\r<BR>\n" );
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document.write( "If both pipes are open, then it would take 36/3 = 12 hours to fill the tank.<BR>\n" );
document.write( "Formula:<BR>\n" );
document.write( "time = (amount done)/(rate)\r<BR>\n" );
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document.write( "Answer: <font color=red size=4>12 hours</font><BR>\n" );
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