# Two cities

The car goes from city A to city B at an average speed of 70 km/h, back at an average speed of 50 km/h. If it goes to B and back at an average speed of 60 km/h, the whole ride would take 8 minutes less. What is the distance between cities A and B?

Result

s =  140 km

#### Solution:

s = 70a
s = 50b
2*s = 60*(a+b-8/60)

70a-s = 0
50b-s = 0
3600a+3600b-120s = 480

a = 2
b = 145 = 2.8
s = 140

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