Algebra.Com's Answer #834962 by ikleyn(52787)![\"\"](\"/images/stars/stars-13.gif\")  
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document.write( "A plane can travel 1,015 miles in 7 hours traveling against the wind.
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document.write( "Traveling with the same wind, the plane can travel 820 miles in 4 hours.
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document.write( "How fast can the plane travel in still air and how fast is the wind current?
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document.write( "Let u be the plane speed in still air,\r\n" );
document.write( "and let v be the rate of the wind.\r\n" );
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document.write( "The effective speed of the plane with the wind is\r\n" );
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document.write( " u + v =  = 205 miles per hour. (1)\r\n" );
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document.write( "The effective speed of the plane against the wind is\r\n" );
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document.write( " u - v =  = 145 miles per hour. (2)\r\n" );
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document.write( "Add equations (1) and (2) and find u\r\n" );
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document.write( " 2u = 205 + 145 = 350, u = 350/2 = 175 miles per hour (the speed of the plane in still air).\r\n" );
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document.write( "From equation (1), find v\r\n" );
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document.write( " v = 205 - 175 = 30 miles per hour (the rate of the wind).\r\n" );
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document.write( "ANSWER. The speed of the plane in still air is 175 miles per hour.\r\n" );
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document.write( " The rate of the wind is 30 miles per hour.\r\n" );
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document.write( "Solved.\r
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