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A can go round a circular path 8 times in 40 minutes. If the diameter of the circle is increased to 10 times the original diameter, the time required by A to go round the new path once travelling at the same speed as before is :
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- 25 min
- 20 min
- 50 min
- 100 min
- 25 min
Correct Option: C
Using Rule 7,
| Circumference = 2πr = | × r metre | |
| 7 |
Distance covered in 8 times = 16πr metres
| ∴ Speed = | |
| Time |
| = | m/minute | |
| 40 |
| = | m/minute | |
| 5 |
New circumference = 2πr × 10 = 20 πr
| ∴ Required time = | × 5 minute = 50 minute | |
| 2πr |
