document.write( "Question 60759: A plane flies 440 miles with the wind and 320 miles against the wind in the same length of time. If the speed of the wind is 30 mph, What is the speed of the plane in still air? \n" ); document.write( "
Algebra.Com's Answer #41823 by ankor@dixie-net.com(22740)\"\" \"About 
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A plane flies 440 miles with the wind and 320 miles against the wind in the same length of time. If the speed of the wind is 30 mph, What is the speed of the plane in still air?
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\n" ); document.write( "The times given for the two distances are the same, so we can make a simple time equation:
\n" ); document.write( ":
\n" ); document.write( "Let s = speed in still air
\n" ); document.write( "(s+30) = speed with the wind
\n" ); document.write( "(s-30) = speed against the wind
\n" ); document.write( "Time = dist/speed
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\n" ); document.write( "440 mi time = 330 mi time
\n" ); document.write( "\"440%2F%28s%2B30%29+=+330%2F%28s-30%29\"
\n" ); document.write( ":
\n" ); document.write( "Cross multiplying result in:
\n" ); document.write( "440(s-30) = 330(s+30)
\n" ); document.write( "440s -13200 = 330s + 9900
\n" ); document.write( "440s - 330s = 9900 + 13200
\n" ); document.write( "110s = 23100
\n" ); document.write( "s = 23100/110
\n" ); document.write( "s = 210 mph is speed of the plane in still air
\n" ); document.write( ":
\n" ); document.write( "It's a good idea to check our solution in the original time equation:
\n" ); document.write( "\"440%2F%28240%29+=+330%2F%28180%29\" do the math here to be sure they are equal
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\n" ); document.write( "Make sense to you? Any questions?\r
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