<PRE><B>Question 943101</B>
A plane can fly 390 mph in still air. If it can fly 220 miles downwind in the same amount of time it can fly 170 miles upwind, find the velocity of the wind.
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let w=speed of wind
390+w=speed of plane downwind
390-w=speed of plane downwind
travel time=distance/speed(same for downwind and upwind)
..
{{{220/(390+w)=170/(390-w)}}}
220(390-w)=170(390+w)
85800-220w=66300+170w
390w=19500
w=50
speed of wind=50 mph</PRE>