document.write( "Question 2627: The current in a stream moves at a speed of 3km/h. A boat travels 40km upstream and 40km downstream in a total time of 14 hours. What is the speed of the boat in still water? \n" ); document.write( "
Algebra.Com's Answer #1146 by kiru_khandelwal(79)\"\" \"About 
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Let the speed of the boat be x km/h
\n" ); document.write( "speed of the stream = 3km/h
\n" ); document.write( "Upstream speed of the boat will be (x-3)km/h
\n" ); document.write( "and downstream speed of the boat will be (x+3)km/h
\n" ); document.write( "Distance travelled upstream = 40km
\n" ); document.write( "Distance travelled downstream = 40km\r
\n" ); document.write( "\n" ); document.write( "Time taked by the boat to go upstream = distance/speed = 40/(x-3)
\n" ); document.write( "Time taken by the boat to go downstream = distance/speed = 40/(x+3)\r
\n" ); document.write( "\n" ); document.write( "So Total time taken will be 40/(x-3) + 40/(x+3)\r
\n" ); document.write( "\n" ); document.write( "But the total time taken is 14 hrs
\n" ); document.write( "so the equation will be
\n" ); document.write( "40/(x-3) + 40/(x+3) = 14
\n" ); document.write( "=> (40(x+3) + 40(x-3))/(x+3)(x-3) = 14
\n" ); document.write( "=> 40(x+3+x-3)= 14(x+3)(x-3)
\n" ); document.write( "=> 40(2x) = 14(x^2 - 3^2)
\n" ); document.write( "=> 20(2x) = 7(x^2 -9)
\n" ); document.write( "=> 40x = 7x^2 -63
\n" ); document.write( "=> 7x^2 - 40x -63 =0
\n" ); document.write( "=> solve the equation for x to get the speed of the boat \n" ); document.write( "
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