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4 bells ring at an interval of 4, 12, 20 and 25 minutes. If they ring together at 8 a.m. then at what time they will ring together?.1. 12 noon2. 1 p.m.3. 11 a.m.4. 2 p.m. |
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Answer» Correct Answer - Option 2 : 1 p.m. Given: 4 bells beep at an interval of 4, 12, 20, and 25.minutes. Beep together at 8 a.m. Concept used: Using LCM method Calculation: 4 = 2 × 2 12 = 2 × 2 × 3 20 = 2 × 2 × 5 25 = 5 × 5 LCM of 4, 12, 20 and 25 = 2 × 2 × 3 × 5 × 5 ⇒ 300 minutes ⇒ 5 hour So, 8 a.m. + 5 hour = 13 p.m. = 1 p.m. ∴ They will beep together again at 1 p.m. |
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