Question

This is totally confusing to me, how do you set this up and solve this problem?
Flying agains the jet stream a jet travels 4200 km in 5 hours. flying wih the jetstream, the same jet travels 10620 km in 9 hours. What is the speed of the jet still in the air, and what is the speed of the jet stream?

Answer 1

The Question

Flying against the jet stream, a jet travels 4200 km in 5 hours. flying with the jetstream, the same jet travels 10620 km in 9 hours. What is the speed of the jet still in the air, and what is the speed of the jet stream?

Concept

When jet moves against the stream, it's speed is decreased. It will be numerically equal to difference between the speeds of jet in still air and stream.

When jet moves with the stream, it's speed is increased . It will be numerically equal to sum of the speeds of jet in still air and stream.

Solution

Supposition

Let the speed of jet in still air is a kmph.

Let the speed of stream is b kmph

Now,

Speed of jet against stream = a - b.

Speed of jet with stream = a + b.

In the question, It's given that,

Jet travels 4200 km against stream in 5 hours.

Using, Speed = Distance / Time.

We get Speed of jet against stream = 840 kmph.

In the question, It's given that,

Jet travels 10620 km with stream in 9 hours.

Using, Speed = Distance / Time.

We get Speed of jet along the stream = 1180 kmph.

We have two equations now,

a - b = 840

a + b = 1180

Solving them gives, a = 1010 , b = 170

Thus, The speed of Jet in still air is 1010kmph And Speed of Stream is 170 kmph