-
A car covers four successive 7 km distances at speeds of 10 km/hour, 20 km/hour, 30 km/
hour and 60 km/hour respectively. Its average speed over this distance is
-
- 30 km/hour
- 20 km/hour
- 60 km/hour
- 40 km/hour
Correct Option: B
Total distance = 7 × 4 = 28 km.
| Total time = |  | + | + | + |  | hours | ||||
| 10 | 20 | 30 | 60 |
| = | | | hours | |
| 60 |
| = | hours = | hours | ||
| 60 | 5 |
| ∴ Average speed = | |
| Total time |
| = | | | kmph | |
| 7/5 |
| = | = 20 kmph | |
| 7 |
