document.write( "Question 408934: I am looking for some hep on this algebra problem for my child please. \r
\n" ); document.write( "\n" ); document.write( "Please show work: The Connecticut River flows at a rate of 4km/h for the length of a popular senic route. In order for a cruiser to travel 60 km upriver and then return in a total of 8 hr, how fast must the boat be able to travel in still water? \n" ); document.write( "
Algebra.Com's Answer #287988 by nerdybill(7384)\"\" \"About 
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The Connecticut River flows at a rate of 4km/h for the length of a popular senic route. In order for a cruiser to travel 60 km upriver and then return in a total of 8 hr, how fast must the boat be able to travel in still water?
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\n" ); document.write( "applying the distance formula:
\n" ); document.write( "d = rt
\n" ); document.write( "solving for time (t) we get:
\n" ); document.write( "t = d/r
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\n" ); document.write( "Let x = speed in still water
\n" ); document.write( "then
\n" ); document.write( "\"time upstream\" + \"time downstream\" = \"total time\"
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\n" ); document.write( "60/(x-4) + 60/(x+4) = 8
\n" ); document.write( "multiplying both sides by (x-4)(x+4) we get:
\n" ); document.write( "60(x+4) + 60(x-4) = 8(x-4)(x+4)
\n" ); document.write( "60x+240 + 60x-240 = 8(x^2-16)
\n" ); document.write( "120x = 8x^2-128
\n" ); document.write( "0 = 8x^2-120x-128
\n" ); document.write( "dividing both sides by 8:
\n" ); document.write( "0 = x^2-15x-16
\n" ); document.write( "factoring:
\n" ); document.write( "0 = (x-16)(x+1)
\n" ); document.write( "x = {16,-1}
\n" ); document.write( "we can throw out the negative solution leaving:
\n" ); document.write( "x = 16 mph\r
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