Question

Flying against the jetstream, a jet travels 3950 miles in 5 hours. Flying with the jetstream, the same jet travels 10,170 miles in 9 hours. What is the rate of thejet in still air and what is the rate of the jetstream?

Answer 1

Velocity of that jet flying against the jetstream is:

$V_1=\frac{3950}{5}=790\text{ miles/hour}$

And the velocity of that jet flying with the jetstream is:

$V_2=\frac{10170}{9}=1130\text{ miles/hour}$

Let the velocity of that jet in still air be x miles per hour and the velocity of jetstream be y miles per hour, so:

$x-y=790$

and

$x+y=1130$

Adding the two equations we have:

$(x-y)+(x+y)=790+1130$$x-y+x+y=1920$$2x=1920$$x=\frac{1920}{2}$$x=960$

the velocity of that jet in still air is 960 miles per hour.

And the rate of the jetstream "y" is (replacing x in the first equation):

$x-y=790$$960-y=790$$y=960-790$$y=170$

170 miles per hour