Question

On a 60 km track,a train travels the first 30 km at a uniform speed of 30 km per hour. How fast the train travels the next 30km so as to have an average of 40 km per hour for the entire trip

Answers

bobpursley
avgvelocity= total distance/total time
total distance=60km
total time=30/30 + 30/v =(v+30)/v

40=60/(v+30)/v
= 60v/(v+30)
40v+1200=60v
v=60km/hr

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