<PRE><B>Question 82147</B>
the speed of an airplane in still air is 257 mph. the plane travels 570 mi against the wind and 1780 with the wind in a total time of 9 hr. what is the speed of the wind?
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Against the wind DATA:
Distance = 570 mi ; Rate = 257-wind ; Time = d/r = 570/(257-w) hr.
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With the wind DATA:
Distance = 1780 mi ; Rate = 257+wind; Time = d/r = 1780/(257+w) hr.
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EQUATION:
time with + time against = 9 hr.
1780/(257+w) + 570/(257-w) = 9
Multiply thru by (257^2-w^2) to get:
1780(257- w) + 570(257 + w) = 9(257^2-w^2)
603950 - 1210w = 594441 - 9w^2
9w^2-1210w+9509 = 0
w = [1210 +- sqrt(1210^2-4*9*9509)]/18
w = [1210+-1059.14]/18
Positive answer: w = 126.06 mph
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Cheers,
Stan H.




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