Question

The speed of a man for the first 4 hours is 35 km/h and for the next 6 hours his speed is 45 km/h, find the ratio of average of speeds to the average speed.
1. 10/11 
2. 21/20
3. 30/31
4. 40/41

Answer 1

Correct Answer - Option 4 : 40/41

Given :

The speed of a man for the first 4 hours is 35 km/h and for the next 6 hours is 45 km/h.

Formula used :

Average speed = Total distance/total time

Average of speed = (sum of all speeds)/Number of different speeds 

Calculations :

Total distance = 4 × 35 + 6 × 45         (distance = speed × time)

⇒ 140 + 270 = 410 km 

Average speed = 410/10     (distance = 410 and time = 4 + 6 = 10 hours)

⇒ 41 km/h 

Now, 

Average of speeds = (35 + 45)/2        (He travelled with speed of 35 km/h and 45 km/h)

⇒ 80/2 = 40 

Now required ratio = 40/41 

∴ Option 4 will be the correct choice.