document.write( "Question 1113103: An airplane travels 1200 miles in 4 hours with the wind. The return trip against the wind takes 5 hours. What is the wind speed and the speed of the airplane in still air? \n" ); document.write( "

Algebra.Com's Answer #728137 by ikleyn(52803) $\"\"$ $\"About$

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document.write( "The speed with the wind was\r\n" );
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document.write( " = 300 miles per hour.\r\n" );
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document.write( "It is the sum of the plane speed at no wind  \"u\"  and speed of the wind  \"v\":\r\n" );
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document.write( "u + v = 300.    (1)\r\n" );
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document.write( "The speed against the wind was\r\n" );
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document.write( " = 240 miles per hour.\r\n" );
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document.write( "It is the difference of the plane speed at no wind  \"u\"  and speed of the wind  \"v\":\r\n" );
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document.write( "u - v = 240.    (2)\r\n" );
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document.write( "Now add equations (1) and (2). You will get\r\n" );
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document.write( "2u = 300 + 240 = 540,   which implies  u =  = 270 mph.\r\n" );
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document.write( "Now substitute it into eq(1) to get\r\n" );
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document.write( "v = 300 - 270 = 30.\r\n" );
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document.write( "Answer.  The plain speed at no wind is 270 mph;  the wind speed is 30 mph.\r\n" );
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\n" ); document.write( "It is a typical \"tailwind and headwind\" word problem.\r
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\n" ); document.write( "\n" ); document.write( "See the lessons \r
\n" ); document.write( "\n" ); document.write( "    - Wind and Current problems \r
\n" ); document.write( "\n" ); document.write( "    - Wind and Current problems solvable by quadratic equations \r
\n" ); document.write( "\n" ); document.write( "    - Selected problems from the archive on a plane flying with and against the wind \r
\n" ); document.write( "\n" ); document.write( "in this site.\r
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\n" ); document.write( "\n" ); document.write( "Also, you have this free of charge online textbook in ALGEBRA-I in this site\r
\n" ); document.write( "\n" ); document.write( "    ALGEBRA-I - YOUR ONLINE TEXTBOOK.\r
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\n" ); document.write( "\n" ); document.write( "The referred lessons are the part of this textbook under the section \"Word problems\", the topic \"Travel and Distance problems\".\r
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\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Save the link to this online textbook together with its description\r
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\n" ); document.write( "\n" ); document.write( "Free of charge online textbook in ALGEBRA-I
\n" ); document.write( "https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson\r
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\n" ); document.write( "\n" ); document.write( "to your archive and use it when it is needed.\r
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