Multiple choice

Four bells toll together at 9.00 am. They toll after 7, 8, 11 and 12 seconds, respectively. How many times will they toll together again in the next 3 hours?

  1. 3

  2. 4

  3. 5

  4. 9

  5. 7
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The LCM of 7, 8, 11 and 12 is 1848. So, the bells will toll together after every 1848 seconds. In 1848 seconds, all four bells toll 1 time. In 3 hrs (3 x 60 x 60), i.e. 10800 seconds, they will toll 3 x 60 x 60/1848 times = 5.84 times. As it has to be an integral part, so the answer is 5.

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