<PRE><B>Question 305701</B>
at cruising speed, and airplane flew 500 kilometers with the wind in the same amount of time it took to fly 400 kilometers against the wind. if the constant speed of the wind is 20kph, what is the cruising speed of the airplane?

let speed be x

With wind  speed = x+20

time = 500 / x+20

against wind it will be x-20

time = 400 /x-20

500 / x+20 = 400 / x-20

500(x-20)=400(x+20)

500x-10000 = 400x+8000

100x = 18000

x= 180 mph



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