document.write( "Question 1107789: Jane took 30 min to drive her boat upstream to​ water-ski at her favorite spot. Coming back later in the​ day, at the same boat​ speed, took her 15 min. If the current in that part of the river is 6 km per​ hr, what was her boat speed in still​ water? \n" ); document.write( "
Algebra.Com's Answer #722820 by mananth(16946)\"\" \"About 
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Jane took 30 min to drive her boat upstream to​ water-ski at her favorite spot. Coming back later in the​ day, at the same boat​ speed, took her 15 min. If the current in that part of the river is 6 km per​ hr, what was her boat speed in still​ water?\r
\n" ); document.write( "\n" ); document.write( "Let boat speed in still water be x
\n" ); document.write( "current speed = 6km/h
\n" ); document.write( "Let distance be y km\r
\n" ); document.write( "\n" ); document.write( "upstream speed = (x-6) km/h.
\n" ); document.write( "downstream speed = (x+6) km/h\r
\n" ); document.write( "\n" ); document.write( "time = distance / speed
\n" ); document.write( "y/(x-6) =1/2 hour
\n" ); document.write( "2y= x-6.............1\r
\n" ); document.write( "\n" ); document.write( "y/(x+6) = 1/4 hour
\n" ); document.write( "4y = x+6...............2
\n" ); document.write( "multiply equation (1) by 2
\n" ); document.write( "we get
\n" ); document.write( "4y= 2x-12...............3\r
\n" ); document.write( "\n" ); document.write( "therefore equation (2) = (3)
\n" ); document.write( "x+6 = 2x-12
\n" ); document.write( "2x-x = 18
\n" ); document.write( "x= 18
\n" ); document.write( " Speed of boat in still water is 18kmh\r
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