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A car moving in the morning fog passes a man walking at 4 km/h. in the same direction. The man can see the car for 3 minutes and visibility is upto a distance of 130 m. The speed of the car is :
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7 3 km. per hour 5 -
6 3 km. per hour 5 - 7 km. per hour
- 5 km. per hour
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Correct Option: B
Speed of car = x kmph.
Relative speed = (x – 4) kmph.
| Time = 3 minutes = | hours = | hours | ||
| 60 | 20 |
Distance = 130 metre
| = | km. = | km. | ||
| 1000 | 100 |
| ∴ Relative speed = | |
| Time |
| ⇒ x – 4 = | × 20 | |
| 100 |
⇒ 5x – 20 = 13
⇒ 5x = 20 + 13 = 33
| ⇒ x = | = 6 | kmph. | ||
| 5 | 5 |
