document.write( "Question 696790: A fisherman can row a boat 8km downstream and return in 100min. If the speed of the stream is 2km per hour, find the speed of the boat in still water? \n" ); document.write( "
Algebra.Com's Answer #429420 by lwsshak3(11628)\"\" \"About 
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A fisherman can row a boat 8km downstream and return in 100min. If the speed of the stream is 2km per hour, find the speed of the boat in still water?
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\n" ); document.write( "let x=speed of boat in still water
\n" ); document.write( "x+2=downstream speed
\n" ); document.write( "x-2=upstream speed
\n" ); document.write( "speed=distance/travel time
\n" ); document.write( "8/(x+2)+8/(x-2)=100/60
\n" ); document.write( "LCD:(x+2)(x-2)
\n" ); document.write( "8(x-2)+8(x+2)=(100/60)*(x+2)(x-2)
\n" ); document.write( "8(x-2+x+2)=100(x+2)(x-2)/60
\n" ); document.write( "240(2x)=100(x^2-4)
\n" ); document.write( "480x=100x^2-400
\n" ); document.write( "100x^2-480x-400=0
\n" ); document.write( "10x^2-48x-40=0
\n" ); document.write( "solve by following quadratic formula:
\n" ); document.write( "\"x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+\"
\n" ); document.write( "a=10, b=-48,c=-40
\n" ); document.write( "ans: x≈5.52
\n" ); document.write( "speed of boat in still water≈5.52 km/hr \n" ); document.write( "
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