Question

On a 60 km straight road,a bus travels the first 30km with a uniform speed of 30kmh .How fast must the bus travel the next 30 km so as to have average speed of 40 kmh for entire trip.
First 30km with a speed of 30km/h means it took 1 hour.

For an average of 40km/h over 60 km, total time = 60/40 = 1.5 hours.

Time left for 30 km = 1.5-1 = 0.5 h.

Can you calculate the speed needed for the second half of the journey?
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Total Time taken t= distance / average speed=60/40=1.5h

Time taken to cover first half T1=30/30=1h
Time taken to cover second half T2=30/V
Now,T=T1+T2=1.5=1+30/V
Then,1.5V=1V+30
30=1.5V-1V
30=0.5V
30/0.5=V
Hence,V=60kmh

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