document.write( "Question 1118535: A motorboat traveling with the current went 72 miles in 3 hours. Against the current, the boat could only go 48 miles in the same amount of time. Find the rate of the current is 4 miles per hour \n" ); document.write( "

Algebra.Com's Answer #733888 by ikleyn(52790) $\"\"$ $\"About$

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document.write( "The effective speed downstream is  = 24 miles per hour.\r\n" );
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document.write( "It is the sum of the motorboat own speed relative to water and the current speed:\r\n" );
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document.write( "24 = u + v     (1)\r\n" );
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document.write( "The effective speed upstream is  = 16 miles per hour.\r\n" );
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document.write( "It is the difference of the motorboat own speed relative to water and the current speed:\r\n" );
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document.write( "16 = u - v.    (2)\r\n" );
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document.write( "Thus you have these two equations\r\n" );
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document.write( "u + v = 24\r\n" );
document.write( "u - v = 16\r\n" );
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document.write( "Add them to get\r\n" );
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document.write( "2u = 24 + 16 = 40  ====>  u = 40/2 = 20\r\n" );
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document.write( "and then from eq(1)  get  v = 24 - 20 = 4.\r\n" );
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document.write( "Answer.  The rate of the current is  4 miles per hour.\r\n" );
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