document.write( "Question 937771: A helicopter flew 15 miles against a 25 mph headwind. Then it flew back with the wind at its tail. The round trip lasted 27 minutes. Find the helicopter's speed in still air.
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\n" ); document.write( "A helicopter flew 15 miles against a 25 mph headwind. Then it flew back with the wind at its tail. The round trip lasted 27 minutes. Find the helicopter's speed in still air.
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document.write( "Let speed in still air be S
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document.write( "Then time taken to fly against the wind = 
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document.write( "Time taken to fly with the wind = 
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document.write( "Since total trip time was 27 minutes, or , or  hr, then: 
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document.write( "15(20)(S + 25) + 15(20)(S – 25) = 9(S – 25)(S + 25) ----- Multiplying by LCD, 20(S – 25)(S + 25)
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document.write( "(S – 75)(3S + 25) = 0
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document.write( "S, or speed in still air =  mph	    OR		   S =  (ignore) \n" );
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