Question

Three bells ring at regular interval first bell rings after 10 minutes seconds after 15 minutes and third Bell after 20 minutes if there are together at 8 o'clock at what time will they ring again together? ​

Answer 1

Answer:

9 o'clock

Step-by-step explanation:

Find the LCM of 10, 15 and 20.

It's LCM is 60.

This implies that the bell will ring after 60 minutes, i.e. 9 o'clock.

Or you could do the Logical way,

1st bell will ring at 8:10, 8:20, 8:30, 8:40, 8:50 & 9:00.

2nd one at 8:15, 8:30, 8:45, 9:00.

3rd at 8:20, 8:40, 9:00.

Above we notice that all of them ring at 9:00, therefore giving us the answer

Answer 2

The LCM of 10,15 and 20 is 60 minutes.
We know,
1 hour=60 minutes.
So,the next time they will ring together is(8 o’clock +1 hour)
=9 o’clock (answer)