Question

Five bells begin to toll together and they toll at intervals of 6, 5, 7, 10 and 12 seconds respectively. How many times they toll together in one hour excluding the one at the start ?
1. 7
2. 8
3. 9
4. 10

Answer 1

Correct Answer - Option 2 : 8

Given:

Five bells begin to toll together and they toll at intervals of 6, 5, 7, 10 and 12 seconds respectively.

Concept used:

LCM method

Calculation:

According to the question,

LCM of the 6, 5, 7, 10, 12 sec

⇒ 420 sec

After every 420 sec bell ring together

In one hour

⇒ 60 × 60/420

⇒ 8

∴ 8 times they toll together in one hour excluding the one at the start.