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A person running at a speed of 4 m/s in a circular track of radius 420 m. If he decrease his speed by 1/4 after completing every one round of track, then what is the time take by him to complete two rounds of the track?1. 1.54 hours2. 1540 seconds3. 1540 minutes4. 1.5 hours 40 minutes5. None of the above/More than one of the above |
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Answer» Correct Answer - Option 2 : 1540 seconds Given: Initial speed of person = 4 m/s Radius of track = 420 m Decrease in speed = 1/4 Calculations: Distance covered in on round = 2 × π × r ⇒ 2 × (22/7) × 420 ⇒ 2,640 m Time taken to complete first round = 2640/4 ⇒ 660 sec After 1 round speed = 4 - {4 × (1/4)} ⇒ 4 - 1 ⇒ 3 m/s Time taken to complete second round = 2640/3 ⇒ 880 sec Total time taken = 660 + 880 ⇒ 1540 sec ∴ The time take by him to complete two rounds of the track 1540 seconds |
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