from one location to another half the time the speed is 60km/hr and another half is 100km/hr then what it is average speed?

Average speed = total distance/total time.

 

Let t be the total time and d be the total distance. Then

 

d = 60*t/2 + 100*t/2

so d = t(30 + 50)

d = t*80

so average speed = d/t = 80 km/hr

 

If the question were 60km/hr for half the distance and 100 km/hr for the other half distance, then

t = d/(2*60) + d/(2*100) 

t = d*(1/120 + 1/200) 

t = d/75

so average speed = d/t = 75 km/hr

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