document.write( "Question 1110188: A boat goes 30km upstream and 44kms downstream in 10hrs.In 13hrs it can go 40kms upstream and 55kms downstream.The speed of the boat in still water is? \n" ); document.write( "

Algebra.Com's Answer #725186 by mananth(16946) $\"\"$ $\"About$

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let speed of boat in still water be x km/h
\n" ); document.write( "y the speed of current
\n" ); document.write( "x+y = speed with current
\n" ); document.write( "x-y = speed against current\r
\n" ); document.write( "\n" ); document.write( "time upstream + time down stream = total time
\n" ); document.write( "
\n" ); document.write( "condition I
\n" ); document.write( "30/(x-y) + 44/(x+y) = 10
\n" ); document.write( "condition II
\n" ); document.write( "40/(x-y) + 55/(x+y) = 13\r
\n" ); document.write( "\n" ); document.write( "Let 1/(x+y) = a and 1/(x-y) =b\r
\n" ); document.write( "\n" ); document.write( "plugging a and b\r
\n" ); document.write( "\n" ); document.write( "30b+ 44a = 10
\n" ); document.write( "40b + 55a=13\r
\n" ); document.write( "\n" ); document.write( "solving the above we get
\n" ); document.write( "a= 1/11 and b = 1/5\r
\n" ); document.write( "\n" ); document.write( "1/(x+y) = 1/11
\n" ); document.write( "1/(x-y) = 1/5
\n" ); document.write( "Therefore x+y = 11
\n" ); document.write( " x-y = 5\r
\n" ); document.write( "\n" ); document.write( "Solve x=8 and y=3 speed in km/h\r
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "

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