SOLUTION: [ A car travels 180 km at 70 km/h and returns to the initial departure point at 60 km/h. Calculate average speed of the car. ]

Question 818285: [ A car travels 180 km at 70 km/h and returns to the initial departure point at 60 km/h. Calculate average speed of the car. ]
Answer by TimothyLamb(4379) (Show Source): You can put this solution on YOUR website!
s = d / t
t = d / s
---
outbound:
ta = d / s
ta = 180/70
---
return:
tb = d / s
tb = 180/60
---
total time:
ta + tb = (180/70) + (180/60)
ta + tb = 5.5414286 hours
---
average speed:
s = d / t
s = (2)(180) / (ta + tb)
s = (360) / (5.5414286)
---
s = 64.615 kph
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