Question

An airplane flew 3.5 hours with a 40 mph head wind. The return trip with a tail wind of the same speed took 2.5 hours. Find the speed of the plane in still air.

240 mph

220 mph

200 mph

180 mph

Answer 1

let speed in still air be x mph
..
speed with head wind = x-40
speed with tail wind = x+40
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Distance = speed * time
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Headwind distance = 3.5(x-40)
Tailwind distance = 2.5(x+40)
..
3.5(x-40) = 2.5(x+40)
3.5x-140=2.5x+100
x=140+100
x=240 mph speed of plane in still air
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