SOLUTION: Flying against the wind, a jet travels 5670mi in 7 hours. Flying with the wind, the same jet travels 11,790mi in 9 hours. What is the rate of the jet in still air and what is the r

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Question 1065217: Flying against the wind, a jet travels 5670mi in 7 hours. Flying with the wind, the same jet travels 11,790mi in 9 hours. What is the rate of the jet in still air and what is the rate of the wind?

Found 2 solutions by josgarithmetic, ikleyn:
Answer by josgarithmetic(39618)   (Show Source): You can put this solution on YOUR website!
RT=D, constant travel rate rule for rate R, time T, distance D. 
r, speed in absence of wind
w, speed of wind


              SPEED     TIME     DISTANCE

WITHWIND      r+w       9        11790

AGAINST       r-w       7         5670


Answer by ikleyn(52797)   (Show Source): You can put this solution on YOUR website!
.
Flying against the wind, a jet travels 5670 mi in 7 hours. Flying with the wind, the same jet travels 11,790 mi in 9 hours.
What is the rate of the jet in still air and what is the rate of the wind?
~~~~~~~~~~~~~~~~~~~~~~~~ 

Let u be the speed of the plane at no wind (in mph),
and "v" be the speed of the wind.

Then

 = u - v    (1)   (speed flying with the wind)

 = u + v   (2)   (speed flying against the wind)

Simplify:


u - v =  810,           (1')
u + v = 1310.           (2')

Add the two equations (1') and (2'). You will get

2u = 2120  ---->  u =  = 1060 mph.

Then from (2') v = 1310 - u = 1310 - 1060 = 250 mph.

Thus the formal answer is: the speed of the plane is 1060 mph, the speed of wind is 250 mph.


     Now, the speed of wind of 250 mph is more that a strongest hurricane,
          so I don't know who invented this problem.

As well as I don't know for whom I solved it and for what.


Usually I have good advises for people who come to the forum with similar problems,
but in this case, I don't know what to do and how to communicate with them.



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