document.write( "Question 574816: A boat can travel at a speed of 12km / h in still water. If it takes three hours to go 15km upstream and back, find the speed of the current. \n" ); document.write( "
Algebra.Com's Answer #369299 by stanbon(75887)\"\" \"About 
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A boat can travel at a speed of 12km / h in still water. If it takes three hours to go 15km upstream and back, find the speed of the current.
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\n" ); document.write( "Upstream DATA:
\n" ); document.write( "rate = 12-c km/h ; distance = 15 km ; time = 15/(12-c) hrs
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\n" ); document.write( "Downstream DATA:
\n" ); document.write( "rate = 12+c km/h ; distance = 15 km ; time = 15/(12+c) hrs
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\n" ); document.write( "Equation:
\n" ); document.write( "time + time = 3 hrs.
\n" ); document.write( "15/(12-c) + 15/(12+c) = 3
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\n" ); document.write( "[15(12+c) + 15(12-c) = 3(144-c^2)
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\n" ); document.write( "360 = 3(144-c^2
\n" ); document.write( "120 = 144-c^2
\n" ); document.write( "c^2 = 24
\n" ); document.write( "c = 2sqrt(6) km/h (speed of the current)
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\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H.
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