document.write( "Question 1084421: A boat sails upstream and after 2 hours it has sailed 10km. if the boat would sail downstream, it would sail 30 km in 2 hours calculate the speed of the boat and of the stream in km/h \n" ); document.write( "

Algebra.Com's Answer #698525 by ikleyn(52786) $\"\"$ $\"About$

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document.write( "The effective speed upstream is  = 5 km/h.\r\n" );
document.write( "It is the difference of the boat speed in still water \"u\" and the rate of stream \"v\":\r\n" );
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document.write( "u - v =  5.    (1)\r\n" );
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document.write( "The effective speed downstream is  = 15 km/h.\r\n" );
document.write( "It is the sum of the boat speed in still water \"u\" and the rate of stream \"v\":\r\n" );
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document.write( "u + v = 15.    (2)\r\n" );
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document.write( "Add the equations (1) and (2). You will get\r\n" );
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document.write( "2u = 5 + 15 = 20,   --->  u =  = 10 km/h.\r\n" );
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document.write( "Thus the speed of the boat in still water is 10 km/h.\r\n" );
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document.write( "Then the speed of the stream is v = 15 - 5 = 15 - 10 = 5 km/h, from equation (2).\r\n" );
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document.write( "Answer.  The speed of the boat in still water is 10 km/h.  The speed of the stream is 5 km/h.\r\n" );
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