Question

A car travels from A to B at a speed of 20 km/h and returns at a speed of 40 km/h . The average velocity of the car for the whole kourney is.


(a) 20/3 km/h
(b) 50/3 km/h
(c) 24 km/h
(d) zero

Answer 1

avg.speed = total distance / total time.

One way distance = xx, say. Then total distance = 2x2x.

Time = distance / speed, so total time =x/60+x/40=x/60+x/40. So here’s what you need:

2xx/60+x/402xx/60+x/40

The x’s cancel. The answer is 48.