Question

A Bike travels the first 1/4 of a certain distance with speed of 10km/hr ,the second 1/4 distance with a speed of 20km/hr , the third 1/4 distance with a speed of 30km/hr and the last 1/4 distance with a speed of 40km /hr the average speed of the bike for whole journey is

Answer 1

Let $\frac{1}{4}th$ of certain distance be $d$

then Total distance travelled = $4d$

Total time taken = $\frac{d}{10}+\frac{d}{20}+\frac{d}{30}+\frac{d}{40}$hrs

So Average speed = $19.2$ Km/Hr