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The time required for a boy to travel along the external and internal boundaries of a circular path are in the ratio 20 : 19. If the width of the path be 5 metres, the internal diameter is :
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- 195 metres
- 192 metres
- 180 metres
- 190 metres
- 195 metres
Correct Option: D
More distance, more time (speed is constant)
| ∴ | = | ||
| 2πr | 19 |
| ⇒ | = | ||
| r | 19 |
⇒ 20r = 19r + 95
⇒ 20r – 19r = 95
⇒ r = 95 metre
∴ Internal diameter = (2 × 95) metre = 190 metre
