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You can put this solution on YOUR website!
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\n" ); document.write( "Flying with the wind, a plane flew 1,120 mi in 4 h.
\n" ); document.write( "Against the wind, the plane required 7 h to fly the same distance.
\n" ); document.write( "Find the rate of the plane in calm air and the rate of the wind.
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document.write( "Let u be the rate of the plane at no wind (in miles per hour)\r\n" );
document.write( "and v be the rate of the wind (in the same units).\r\n" );
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document.write( "Then the effective rate of the plane with the wind is u + v\r\n" );
document.write( "and the effective rate of the plane against the wind is u - v.\r\n" );
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document.write( "From the problem, the effective rate of the plane with the wind is the distance of 1120 miles \r\n" );
document.write( "divided by the time of 4 hours {{1120/4}}} = 280 mph.\r\n" );
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document.write( " The effective rate of the plane against the wind is the distance of 1120 miles \r\n" );
document.write( "divided by the time of 7 hours 
= 160 mph.\r\n" );
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document.write( "So, we have two equations to find 'u' and 'v'\r\n" );
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document.write( " u + v = 280, (1)\r\n" );
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document.write( " u - v = 160. (2)\r\n" );
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document.write( "To solve, add equations (1) and (2). The terms 'v' and '-v' will cancel each other, and you will get\r\n" );
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document.write( " 2u = 280 + 160 = 440 ---> u = 440/2 = 220.\r\n" );
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document.write( "Now from equation (1)\r\n" );
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document.write( " v = 280 - u = 280 - 220 = 60.\r\n" );
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document.write( "ANSWER. The rate of the plane in still air is 220 mph. The rate of the wind is 60 mph km/h.\r\n" );
document.write( "\r\n" ); document.write( "\n" ); document.write( "Solved.\r
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\n" ); document.write( "\n" ); document.write( "My solution produces the same answer as in the post by @mananth, but makes it in clean, clear and correct form,
\n" ); document.write( "while calculations in the post by @mananth contradict to each other literally in every line.\r
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\n" ); document.write( "\n" ); document.write( "We, the tutors, write here our solutions not only to get certain numerical answer.
\n" ); document.write( "We write to teach - and, in particular, to teach writing solutions in accurate and clear style.\r
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\n" ); document.write( "\n" ); document.write( "@mananth repeats his construction of solution with no change for all similar problems on flies
\n" ); document.write( "with and against the wind simply because his COMPUTER CODE is written this way.
\n" ); document.write( "But his computer code is written in a bad style. It is simply DEFECTIVE.
\n" ); document.write( "But @mananth does not change it just during several ( five or seven or even more ) years.
\n" ); document.write( "My impression of his writing is that he does not read what his code produces, because it is not interesting to him.\r
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\n" ); document.write( "\n" ); document.write( "To me, it is monstrous style posting to the forum.\r
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