document.write( "Question 187675: An airplane flew for 4hr with a 20-mph tailwind. The return flight against the same wind took 5 hr. Find the speed of the plane in still air.
\n" ); document.write( "Can anyone help me? I do not know how to even start.
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Algebra.Com's Answer #140708 by stanbon(75887) $\"\"$ $\"About$

You can put this solution on YOUR website!
An airplane flew for 4hr with a 20-mph tailwind. The return flight against the same wind took 5 hr. Find the speed of the plane in still air.
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\n" ); document.write( "With the wind DATA:
\n" ); document.write( "time = 4 hr: distance = x miles; rate = d/t = x/4 mph
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\n" ); document.write( "Against the wind DATA:
\n" ); document.write( "time = 5 hr. distance = x miles ; rate = x/5 mph
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\n" ); document.write( "Equations:
\n" ); document.write( "p + 20 = x/4
\n" ); document.write( "p - 20 = x/5
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\n" ); document.write( "2p = (x/4)+(x/5)
\n" ); document.write( "2p = 9x/20
\n" ); document.write( "p = 9x/40
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\n" ); document.write( "Substitute into p + 20 = x/4 to solve for \"x\"
\n" ); document.write( "(9x/40) + 20 = (x/4)
\n" ); document.write( "Multiply thru by 40 to get:
\n" ); document.write( "9x + 800 = 10x
\n" ); document.write( "x = 800
\n" ); document.write( "x = 800 (distance traveled)
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\n" ); document.write( "Subtitute to solve for \"p\":
\n" ); document.write( "p = x/4 = 800/4 = 200 mph (plane's speed in still air)
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\n" ); document.write( "Cheers
\n" ); document.write( "Stan H.
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