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Two bullets were fired at a place at an interval of 12 minutes. A person approaching the firing point in his car hears the two sounds at an interval of 11 minutes 40 seconds. The speed of sound is 330 metres per second. What is the approximate speed of the car?
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- 34 kmph
- 32 kmph
- 36 kmph
- 38 kmph
Correct Option: A
If the car were not moving, the person would have heard the two sounds at an interval of 12 minutes. Therefore, the distance travelled by car in 11 minutes 40 seconds is equal to the distance that could have been covered by sound in 12 min – 11 min. 40 seconds = 20 seconds.
Distance covered by sound in 20 seconds
= 330 × 20 = 6600 m
In 11 min 40 seconds
or 700 seconds the car travels 6600 m.
In 1 second the car will travel
| metre = | metre | ||
| 700 | 7 |
| ∴ | metre per second | |
| 7 |
| = | × | km per hr. | ||
| 7 | 5 |
| = | km per hr. | |
| 35 |
| = 33 | km per hr. ≈ 34 kmph | |
| 35 |
