Question

Three bells ring at the interval of 7, 10 and 12 seconds. They start ringing simultaneously at 2:00 pm. At what time will they ring again simultaneously?
1. 3 : 10 pm
2. 3 : 30 pm
3. 2 : 07 pm
4. 2 : 30 pm

Answer 1

Correct Answer - Option 3 : 2 : 07 pm

Given:

Three bells ring at the interval of 7, 10 and 12 seconds and they ring simultaneously at 2:00 pm.

Calculation:

Three bells rings at the interval of 7, 10 and 12 seconds and to calculate the time at which the bells ring again simultaneous we take the LCM of the given time intervals.

LCM of (7, 10 and 12) = 2 × 2 × 3 × 5 × 7 = 420 seconds = 7 minutes

∴ Three bells ring again after 7 minutes.

So, the time at which three bells ring again simultaneously = 2:00 pm + 7 min = 2:07 pm.