SOLUTION: A car has to cover a distance of 10km.It covers a distance of first 4km at a speed 40km/h.How fast should the car travel while covering the remaining distance so that its average s

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Question 881548: A car has to cover a distance of 10km.It covers a distance of first 4km at a speed 40km/h.How fast should the car travel while covering the remaining distance so that its average speed for the entire trip is 60km/h?
Answer by josgarithmetic(39631) About Me  (Show Source):
You can put this solution on YOUR website!
TotalDistance%2FTotalTime=AverageSpeed

10%2F%284%2F40%2B6%2Fr%29=60, all units based on kilometers, hours. r is for travel speed for the last 6 kilometers.

10%2F%281%2F10%2B6%2Fr%29=60

1%2F%281%2F10%2B6%2Fr%29=6

1%2F%28r%2F10r%2B60%2F10r%29=6

1%2F%28%28r%2B60%29%2F%2810r%29%29=6

10r%2F%28r%2B60%29=6

10r=6r%2B360

4r=360

highlight%28r=90%29