SOLUTION: Q. A jet made a trip to the maintenance facility and back. The trip there took three hours and the trip back took four hours. It averaged 120km/h faster on the trip there than on t

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Question 862301: Q. A jet made a trip to the maintenance facility and back. The trip there took three hours and the trip back took four hours. It averaged 120km/h faster on the trip there than on the return trip. Find the jet's average speed on the outbound trip.
I know the answer is 480 miles on the answer sheet, but I'm really confused why
doing
3(x+120) = 4x
isnt the same thing as
4(x-120)=3x
doesn't it mean the same thing?
Thanks
Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
4(x-120)=3x
4x-480-3x
x-480=0
x=480
x is the speed on the outbound trip
x-120=360 return trip

3(y+120) = 4y
3y+360=4y
360=y the return
y+120=480 the outbound trip there
y is average speed on the return trip
Which should you use?
If you are only interested in the outbound then use the first 4(x-120)=3x
If you are only interested in the return then use the second 3(y+120) = 4y
If you want to find out both speeds then it doesn't matter which one you use.