document.write( "Question 22643: a boat takes 2 hours longer to go 45 miles up a river than to return. If the boat's speed in still water is 12 mph, what is the rate of the current \n" ); document.write( "
Algebra.Com's Answer #11602 by AnlytcPhil(1806)\"\" \"About 
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a boat takes 2 hours longer to go 45 miles up a river than to return. If\r\n" );
document.write( "the boat's speed in still water is 12 mph, what is the rate of the current\r\n" );
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document.write( "Let x = the rate of the current.\r\n" );
document.write( "Therefore the boat's rate going against the current is slowed down by x mph\r\n" );
document.write( "or 12-x\r\n" );
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document.write( "Similarly the boat's rate returning with the current is sped u by x mph\r\n" );
document.write( "or 12+x\r\n" );
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document.write( "Make this chart\r\n" );
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document.write( "              Distance |  Rate  |     Time\r\n" );
document.write( "_______________________|________|_____________\r\n" );
document.write( "Going       |          |        |                 \r\n" );
document.write( "Returning   |          |        |            \r\n" );
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document.write( "Fill in the two rates, 12-x going and 12+x returning:\r\n" );
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document.write( "              Distance |  Rate  |     Time\r\n" );
document.write( "_______________________|________|_____________\r\n" );
document.write( "Going       |          |  12-x  |                 \r\n" );
document.write( "Returning   |          |  12+x  |            \r\n" );
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document.write( "Fill in the distances, both of which are 45 miles\r\n" );
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document.write( "              Distance |  Rate  |     Time\r\n" );
document.write( "_______________________|________|_____________\r\n" );
document.write( "Going       |    45    |  12-x  |                 \r\n" );
document.write( "Returning   |    45    |  12+x  |            \r\n" );
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document.write( "Now use TIME = DISTANCE/RATE to fill in the two times.\r\n" );
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document.write( "              Distance |  Rate  |     Time\r\n" );
document.write( "_______________________|________|_____________\r\n" );
document.write( "Going       |    45    |  12-x  |   45/(12-x)     \r\n" );
document.write( "Returning   |    45    |  12+x  |   45/(12+x)\r\n" );
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document.write( "Now use the part that we haven't yet used to make the equation:\r\n" );
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document.write( ">>...a boat takes 2 hours longer to go 45 miles up a river than to return...<<\r\n" );
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document.write( "Therefore \r\n" );
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document.write( "TIME GOING = TIME RETURNING + 2 HOURS\r\n" );
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document.write( "45/(12-x) = 45/(12+x) + 2\r\n" );
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document.write( "Can you solve that?\r\n" );
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document.write( "If not post again\r\n" );
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document.write( "Answers: x = 3 and x = -48\r\n" );
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document.write( "We discard the negative answer.  The rate of the current is 3 mph.\r\n" );
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document.write( "Edwin\r\n" );
document.write( "AnlytcPhil@aol.com
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