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A boy rides his bicycle 10km at an average speed of 12 km/hr and again travels 12 km at an average speed of 10 km/hr. His average speed for the entire trip is approximately :
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- 10.4 km/hr
- 10.8 km/hr
- 11.0 km/hr
- 12.2 km/hr
Correct Option: B
Total distance = 10 + 12 = 22 km
| Total time = | + | ||
| 12 | 10 |
| = | hours | |
| 120 |
| ∴ Required average speed = | |
| Total time |
| = | |||||
| 120 | |||||
| = | × 120 = 10.8 km/hr. | |
| 244 |
Second Method :
Here, d1 = 10, S1 = 12
d2 = 12, S2 = 10
| Average Speed = | |||||
| + | |||||
| S1 | S2 | ||||
| = | |||||
| + | |||||
| 12 | 10 | ||||
| = | = 10.8 km/hrs. | |
| 244 |
