Question

A man drives 15 km towards north in 2 hour, then he turns to east and travels in the same direction for another 2 hours, if the average speed for the whole journey is 10 km/hr, find the rate at which it travels eastwards.
1. 12.5 km/hr
2. 15 km/hr
3. 12 km/hr
4. 40 km/hr
5. 20 km/hr

Answer 1

Correct Answer - Option 1 : 12.5 km/hr

Given:

Average speed = 10 km/hr

Formula Used:

Average speed = Total distance traveled/Total time

Speed = distance/ Time

Calculations:         

Let the distance traveled towards east direction be x km.

Total distance = (15 + x) km

Total Time = (2 + 2) hrs

Average speed = (15+x)/4 = 10

⇒ 15 + x = 40

⇒ x = 25 km

The distance traveled towards east direction =  25 km

Speed = 25/2 = 12.5 km/hr