document.write( "Question 1102182: A pilot flew his single-engine airplane 60 miles with the wind from City A to above City B. He then turned around and flew back to City A against the wind. If the wind was a constant 30 miles per hour, and the total time going and returning was 1.3 hours, find the speed of the plane in still air. \n" ); document.write( "

Algebra.Com's Answer #716833 by ikleyn(52781) $\"\"$ $\"About$

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document.write( "Let x be the speed of plane at no wind\", in miles per hour (mph).\r\n" );
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document.write( "Then the speed with the wind is (x+30) mph,\r\n" );
document.write( "     the speed against the wind is (x-30) mph.\r\n" );
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document.write( "Then the \"time equation\" is\r\n" );
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document.write( " +  = 1.3   hours.\r\n" );
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document.write( "60*(x+30) + 60*(x-30) = 1.3*(x^2-900)  ====>\r\n" );
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document.write( "120x = 1.3x^2 - 1.3*900  ====>  1.3x^2 - 120x - 1.3*900 = 0  ====>\r\n" );
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document.write( " =  = .\r\n" );
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document.write( "Only positive root makes sense  x =  = 101.2.\r\n" );
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document.write( "Answer.  The speed of the plane \"at no wind\" is 101.2 miles per hour.\r\n" );
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