A plane can fly 140 mph in calm air. Flying with the wind, the plane can fly 700 mi in the same amount of time it takes to fly 420 mi against the wind. Whats the rate of the wind?

Answer 1

Let V be the wind speed. The flight time is D/(140+V)with a tail wind and
D/(140-V) with a head wind.

Solve 700/(140+V) = 400/(140-V)
98,000 -700V = 56,000 +400V
1100V = 42,000
V = 38.2 km/h

Answer 2

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