Question

A jet flew east a distance of 1,800 mi with the jetstream in 3 hr. Returning west, against the jetstream, the jet took 4hr. FInd the jet's speed in still air and the rate of the jetstream.

Answer 1

Let the Jet's speed in still air is x mi/hr. and the rate of the jetstream is y mi/hr.

Then we have,

Speed with jetstream = (x + y) mi/hr.

Speed against jetstream = (x - y) mi/hr.

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Now as distance = (speed) * (time), so according to the given data, we have,

3(x + y) = 1800

i.e. x + y = 600.......... (1)

And, 4(x - y) = 1800

i.e. x - y = 450..........(2)

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Now (1) + (2) gives,

x + y + x - y = 600 + 450

i.e. 2x = 1050

i.e. x = 525

So from (1), y = 600 - 525 = 75

.

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So the Jet's speed in still air is 525 miles per hour​​​​​​

And, the rate of jetstream is 75 miles per hour