A jet travels 3860mi against a jetstream in 5 hours and 4610mi with the jetstream in the same amount of time.

Question

A jet travels
3860mi
against a jetstream in
5
hours and
4610mi
with the jetstream in the same amount of time. What is the rate of the jet in still air and what is the rate of the jetstream?

Answer 1

Let x = speed of plane in still air

     y = speed of jetstream

 

Speed with jetstream = x+y

Speed against jetstream = x - y

 

Distance = (Rate)(Time), so Time = Distance/Rate

 

4610/(x+y) = 5   so, 5x + 5y = 4610

3860/(x-y) = 5    so, 5x - 5y = 3860

 

Add the equations to get 10x = 8470

 

Therefore, x = 847 mph (fast plane!)

 

Replace x by 847 in either one of the original equations:

 

   5(847) + 5y = 4610

 

                5y = 375

 

                  y = 75 mph

 

Answer:  The speed of the plane in still air is 847 mph and the speed of              the jetstream is 75 mph.