Question

Two bicycle riders made a 30 km trip in the same time. Cyclist A traveled continuously at an average speed of 20 km/h. Cyclist B traveled continuously except for a 20 min. rest break. What was B’s average speed for the time of actual riding ?

Answer 1

Answer : The average speed of cyclist B is 25.714 km/hr

Explanation :

First we have to convert average speed from km/hr to m/s.

Conversion used :
`km/hr=(5)/(18)m/s`

As we are given the average speed of cyclist A 20 km/hr. The average speed in m/s is:

As,
`1km/hr=(5)/(18)m/s`

So,
`20km/hr=20* (5)/(18)m/s=5.555m/s`

Now we have to calculate the time taken by cyclist A to travel the distance.

`Speed=(Distance)/(Time)`

`5.555m/s=(30000m)/(Time)`

`Time=(30000m)/(5.555m/s)`

`Time=5400s`

conversion used : (1 min = 60 sec)

`Time=(5400)/(60)=90min`

As per question, cyclist B travels same distance in same time but he took rest for 20 min. That means,

Time taken by cyclist B = 90 min - 20 min = 70 min

Now we have to calculate the average speed of cyclist B.

`Speed=(Distance)/(Time)`

`Speed=(30km)/(70min)`

`Speed=(30km)/(((70)/(60)hr))`

conversion used : (1 hr = 60 min)

`Speed=25.714km/hr`

Therefore, the average speed of cyclist B is 25.714 km/hr