A car covers four successive three km stretches at speed of 10 km/hr, 20 km/hr, 30 km/hr and 60 km/hr. respectively. Its average speed over this distance is?
Correct Answer: 20 km/hr .
Explanation:
Total time taken = (3/10 + 3/20 + 3/30 + 3/60) hrs.
= 3/5 hrs. ∴ Average speed = {12 / (3 / 5)} km/hr.
= (12 x 5 ) / 3 km/hr.
= 20 km/hr.
