A car covers four successive 8 km distances at speeds of 12 km/hr, 18 km/hr, 24 km/hr and 36 km/hr, respectively. Its average speed (in km/hr) over this distance is:
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 19.2.
Distances: 4 × 8 km = 32 km
Times: 8/12 + 8/18 + 8/24 + 8/36 = 2/3 + 4/9 + 1/3 + 2/9 = 15/9 = 5/3 hrs
Average speed = 32 ÷ (5/3) = 32 × 3/5 = 19.2 km/hr