document.write( "Question 743104: An airplane flying against the wind travels 165 miles in the same amount of time it would take the same plane to travel 195 miles with the wind. If the wind speed is a constant 30 miles per hour, how fast would the plane travel in still air? \r
\n" ); document.write( "\n" ); document.write( "I think the answer is 180, but my homework says it's incorrect? Why? \n" ); document.write( "

Algebra.Com's Answer #452826 by ankor@dixie-net.com(22740) $\"\"$ $\"About$

You can put this solution on YOUR website!
An airplane flying against the wind travels 165 miles in the same amount of time it would take the same plane to travel 195 miles with the wind.
\n" ); document.write( " If the wind speed is a constant 30 miles per hour, how fast would the plane travel in still air?
\n" ); document.write( ":
\n" ); document.write( "Let s = speed in still air
\n" ); document.write( "then
\n" ); document.write( "(s-30) = ground speed against the wind
\n" ); document.write( "and
\n" ); document.write( "(s+30) = ground speed with the wind
\n" ); document.write( ":
\n" ); document.write( "Write a time equation; time = dist/speed
\n" ); document.write( "time against = time with
\n" ); document.write( " $\"165%2F%28%28s-30%29%29\"$ = $\"195%2F%28%28s%2B30%29%29\"$
\n" ); document.write( "Cross multiply
\n" ); document.write( "195(s-30) = 165(s+30)
\n" ); document.write( "195s - 5850 = 165s + 4950
\n" ); document.write( "195s - 165s = 4950 + 5850
\n" ); document.write( "30s = 10800
\n" ); document.write( "s = 10800/30
\n" ); document.write( "s = 360 mph in still air (you were half right!)
\n" ); document.write( ":
\n" ); document.write( ":
\n" ); document.write( "Confirm this, find the actual time each way, should be equal
\n" ); document.write( "165/330 = .5 hrs
\n" ); document.write( "195/390 = .5 \n" ); document.write( "

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