document.write( "Question 1142254: A pilot flies 1050 mi with a tailwind of 20mph. Against the wind, he flies only 850 mi in the same amount of time. What is the speed of the plane in still air? \n" ); document.write( "

Algebra.Com's Answer #762950 by ikleyn(52790) $\"\"$ $\"About$

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document.write( "If x is the speed of the plane at no wind (in miles per hour), then\r\n" );
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document.write( "    the effective ground speed with the wind is (x+20) mph, while \r\n" );
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document.write( "    the effective ground speed against the wind is (x-20) mph.\r\n" );
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document.write( "The \"time\" equation then is\r\n" );
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document.write( "     = ,\r\n" );
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document.write( "according to the condition   (same amount of time for each flight).\r\n" );
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document.write( "To solve it, cross multiply and simplify\r\n" );
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document.write( "    1050*(x-20) = 850*(x+20)\r\n" );
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document.write( "    1050x - 1050*20 = 850x + 850*20\r\n" );
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document.write( "    1050x - 850x = 850*20 + 1050*20\r\n" );
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document.write( "    x =  = 190.\r\n" );
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document.write( "ANSWER.  The speed of the plane at no wind is 190 miles per hour.\r\n" );
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document.write( "CHECK.    =  = 5 hours;    =  = 5 hours.    ! Correct !\r\n" );
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\n" ); document.write( "\n" ); document.write( "The lesson to learn from this solution and the things to memorize are :\r
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document.write( "    1.  The effective speed of a plane flying with    a wind is the sum        of the two speeds.\r\n" );
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document.write( "    2.  The effective speed of a plane flying against a wind is the difference of the two speeds.\r\n" );
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document.write( "    3.  It gives you a \"time\" equation, which you easily can solve and find the unknown plane' speed.\r\n" );
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