Question

Three bells ring at intervals of 15, 20 and 30 minutes respectively. If they all ring at 11.00

a.M. Together, at what time will they next ring together?

Answer 1

Answer:

Factorise the time of ringing

15 = 3 * 5

20 = 2 * 2 * 5

30 = 2 * 3 * 5

LCM = 5 * 3 * 2 * 2 = 60

Hence, the bell will again ring at the same time after 60 minutes. It rang at 12:00 noon and hence will ring at 1:00 pm again.

Answer 2

Answer:

Fatorise the time ringing.

Step-by-step explanation:

first we take the LCM of 15,20,30

5 |15,20,30

3 | 3, 4 ,6

2 | 1, 4, 2

| 1, 2, 1

therefore, LCM = 5×3×2×2

= 60min

i.e., 12p.m the bell ring again