Question

three alarm clocks ring at intervals of 6, 15 and 20 minutes. If three rang together at 7am then after what time they ring together again.​

Answer 1

Answer:

they rang at 8am

to find it we have to find Lcm of 6,15,20

6=2×3

15=3×5

20=2×2×5

Lcm=(2)2×3×5=60

Answer 2

Answer:

They will next ring at 8 am

Step-by-step

6 = 2*3

15 = 3*5

20 = 2*2*5

In this case it is advised to take Least Common Multiple of these

three numbers

LCM = Highest powers of the common multiple * left no with lest powers

LCM = 2^2*5*3

=4*15

=60 minutes

Given in question they start at 7 am and next at 8 am (60 min = 1 hour) they will ring