Question

A person divides his total route of journey into three equal parts and travels at the speed of 40kmph,30kmph and 15 kmph respectively. what is the average speed of the whole journey?

Answer 1

Answer:

The average speed of the whole journey is 24 km/h

Explanation:

The formula to calculate the average speed is

$\boxed{\text{Average speed}=\frac{\text{Total Distance}}{\text{Total Time}}}$

If one part of the distance is d km

Then total distance = 3d

Time taken in the first part = d/40 hr

Time taken in the second part = d/30 hr

Time taken in the third part = d/15 hr

Total time taken

$=\frac{d}{40}+\frac{d}{30}+\frac{d}{15}$

$=\frac{3d+4d+8d}{120}$

$=\frac{15d}{120}$ hr

Therefore, Average speed

= total distance/total time

=$\frac{3d}{15d/120}$

$=3d\times\frac{120}{15d} =24$ km/hr