Question

A boy walks 5 ķm at vkm/hr. He then cycles 15 km at 2v km/hr. In terms of v, write down the time taken in hours

1. When walking
2. If the total time for journey is 2h 35min, find the boy's walking speed​

Answer 1

The time when walking is 5/v hours

The walking speed is 4 26/31 km/hr

Explanation:

Mathematically;

time = distance/speed

So the time taken when walking will be;

5/v

The time taken when cycling will be:

15/2v

The term 2h 35 minutes is same as 2 35/60

= 2 7/12

If we add the whole times together, we get 2 7/12

Thus;

5/v + 15/2v = 2 7/12

5/v + 15/2v = 31/12

(10 + 15)/2v = 31/12

25/2v = 31/12

12 * 25 = 2v * 31

31v = 6 * 25

v = 150/31

= 4 26/31