A car covers 15 km, 20 km, 30 km and 12 km at speeds of 20 km/h, 30 km/h, 40 km/h and 30 km/h, respectively. The average speed of the car for the total journey is:
Show answer & explanation
Correct answer: C
Explanation
The correct answer is Option 3 i.e 30 km/h.
| Understanding/Application |
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Time taken by the car to cover 15 km at the speed of 20 km/h = 15/20 h Time taken by the car to cover 20 km at the speed of 30 km/h = 20/30 h Time taken by the car to cover 30 km at the speed of 40 km/h = 30/40 h Time taken by the car to cover 12 km at the speed of 30 km/h = 12/30 h Total time taken = 15/20 + 20/30 + 30/40 + 12/30 = 308/120 = 77/30 h |
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Average speed of the car = 77/77/30 = (77 × 30)/77 = 30 km/h |