During a journey of 120 km, Rahi drives first 60 km at the speed of 60 km/h, next 30 km at 60 km/h and the remaining 30 km at the speed of 30 km/h. Determine the average speed.

48 km/h

Distance = Speed × Time

Time  1 = \(\frac{Distance }{Speed}\)

= \(\frac{60 }{60}\) = 1 hour

Time 2 = \(\frac{30 }{60}\) = 0.5 hour

Time 3 = \(\frac{30 }{30}\) = 1 hour

Average speed = \(\frac{120 }{1 + 0.5 + 1}\) 

= \(\frac{120 }{2.5}\) 

= 48 km/h