Two alarm clocks ring their alarms at regular intervals of 90 seconds and 44 seconds. If they first beep together at 6:00 pm, at what time will they beep together for the next time?

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  1. 6:35pm
  2. 6:34pm
  3. 6:36pm
  4. 6:33pm

Answer (Detailed Solution Below)

Option 4 : 6:33pm
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यूपी पुलिस SI (दरोगा) सामान्य हिंदी मॉक टेस्ट
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Detailed Solution

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Given:

Alarm 1 interval = 90 seconds

Alarm 2 interval = 44 seconds

First beep together at 6:00 PM

Formula Used:

Time for next beep together = LCM (Least Common Multiple) of the intervals

Calculation:

LCM of 90 and 44:

Prime factorization of 90 = 2 × 32 × 5

Prime factorization of 44 = 22 × 11

LCM = Product of the highest powers of all prime factors

LCM = 22 × 32 × 5 × 11 = 1980 seconds

1980 ÷ 60 = 33 minutes and 0 seconds

Next beep together = 6:00 PM + 33 minutes

⇒ Next beep together = 6:33 PM

∴ The correct answer is option 4.

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