SOLUTION: a car completes a journey at an average speed of 40 m.p.h. at what speed must it travel on the return journey if the average speed for the complete journey (out and back) is 60 m.p

Question 912045: a car completes a journey at an average speed of 40 m.p.h. at what speed must it travel on the return journey if the average speed for the complete journey (out and back) is 60 m.p.h.?
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
a car completes a journey at an average speed of 40 m.p.h. at what speed must it travel on the return journey if the average speed for the complete journey (out and back) is 60 m.p.h.?
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d/40 + d/r = 2d/60
1/40 + 1/r = 1/30
(r+40)/40r = 1/30
r+40 = 4r/3
3r+120 = 4r
r = 120 mi/hr

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