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4 bells ring at intervals of 30 minutes, 1 hour, 11/2 hour and 1 hour 45 minutes respectively. All the bells ring simultaneously at 12 noon. They will again ring simultaneously at :
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- 12 mid night
- 3 a.m.
- 6 a.m.
- 9 a.m.
Correct Option: D
| 1 | hours = 90 minutes | 2 |
1 hour and 45 minutes = 105 minutes
1 hour = 60 minutes
∴ LCM of 30 minutes, 60 minutes, 90 minutes and 105 minutes
∴ LCM = 3 × 5 × 2 × 2 × 3 × 7 = 1260 minutes
| 1260 minutes = | = 21 hours | 60 |
∴ The bell will again ring simultaneously after 21 hours.
∴ Time will be = 12 noon + 21 hours = 9 a.m.
Required Time will be 9 a.m.
