Question

Three alarm clocks ring at intervals of 4,12 and 20 minutes respectively. if start ringing together, after how much time will they next ring together?

Answer 1

For this, we will first find the LCM or Lowest Common Multiples of the 3 numbers.

It is 60.

So they will ring together after 60 minutes.

Answer 2

This sis a question on LCM.

we need to find the LCM of 4, 12 , 20

We use Prime factorization to get the LCM.

The prime factors are as follows:

4 = 2 × 2

20 = 2 × 2 × 5

12 = 2 × 2 × 3

The LCM is thus:

2 × 2 × 3 × 5 = 60

The bells ring together after 60 minutes.

This is equivalent to 1 hr.