document.write( "Question 548514: The current of a stream moves at a speed of 5km/hr. The boat travels 31 km upstream and 31 km downstream in a total time of 11 hours. What is the speed of the boat in still water? \n" ); document.write( "
Algebra.Com's Answer #357036 by stanbon(75887)\"\" \"About 
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The current of a stream moves at a speed of 5km/hr. The boat travels 31 km upstream and 31 km downstream in a total time of 11 hours. What is the speed of the boat in still water?
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\n" ); document.write( "Upstream DATA:
\n" ); document.write( "distance = 31 km ; rate = b-5 km/hr ; time = d/r = 31/(b-5)hrs
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\n" ); document.write( "Downstream DATA:
\n" ); document.write( "distance = 31 km ; rate = b+5 km/hr ; time = d/r = 31/(b+5) hrs\r
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\n" ); document.write( "Equation:
\n" ); document.write( "31/(b-5) + 31/(b+5) = 11
\n" ); document.write( "31(b+5) + 31(b-5) = 11(b^2-25)
\n" ); document.write( "62b = 11b^2-275
\n" ); document.write( "11b^2 - 62b -275 = 0
\n" ); document.write( "positive solution: b = 8.58 km/hr (speed of boat in still water)
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\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H.
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