Question

If the first one-third of a journey is travelled at 20km/h,next one-third at 40km/h and the last one-third at 60km/h. The average speed of whole journey

Answer 1

Answer:

32.7 km/h

Explanation:

Let the total distance be 3x.

The first one third will be x. Corresponding time for that would be t1,

then t1=distance/speed=x/20

similiarly t2=x/30

and t3=x/40

Now average speed= (total distance)/(total time)

Therefore, v=$\frac{3x}{x/20+x/30+x/40}$

v=$\frac{20*30*40}{20*30+30*40+40*20}$

v=$\frac{14400}{4400}$

v=32.7  km/h