# Its Average Speed Over this Distance is :

A car covers four successive 7 km distances at speeds of 10 km/hour, 30 km/hour, 60 km/hour respectively, Its average speed over this distance is

- 20 km/hour
- 60 km/hour
- 30 km/hour
- 40 km/hour

**Answer is (1): 20 km/hour**

**Explanation:-**A car covers four successive 7 km distances at the speeds of 10 km/hour, 20 km/hour, 30 km/hour and 60 km/hour respectively,

Then, the total time taken by four cars to covered the distance 7 km = 7/10 + 7/20 + 7/30 + 7/60

= (7 x 6 + 7 x 3 + 7 x 2 + 7 x 1)/60

= (42 + 21 + 14 + 7)/60

= 84/60

= 7/5 hours

The total distance covered by four cars = 7 + 7 + 7 + 7

= 28 km

Then, the average speed of four cars = 28/(7/5)

= 28 x 5/7

= 4 x 5

= 20 km/hr

Hence, the answer is (1) 20 km/hr.