document.write( "Question 101185: Ellen's motorboat can travel 30 mi/h in still water. If the boat can travel 7 miles downstream in the same amount of time it takes to travel 3 miles upstream, what is the rate of the river's current? \n" ); document.write( "
Algebra.Com's Answer #73646 by stanbon(75887)\"\" \"About 
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Ellen's motorboat can travel 30 mi/h in still water. If the boat can travel 7 miles downstream in the same amount of time it takes to travel 3 miles upstream, what is the rate of the river's current?
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\n" ); document.write( "Let the river rate be \"c\".
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\n" ); document.write( "Down stream DATA:
\n" ); document.write( "Rate = 30+c ; distance = 7 mi ; time = d/r = 7/(30+c)
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\n" ); document.write( "Up stream DATA:
\n" ); document.write( "Rate = 30-c ; distance = 3 mi : time = d/r = 3/(30-c)
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\n" ); document.write( "EQUATION:
\n" ); document.write( "7/(30+c) = 3/(30-c)
\n" ); document.write( "210-7c = 90+3c
\n" ); document.write( "10c = 30
\n" ); document.write( "c = 3 mph (speed of the current)
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\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H.\r
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