Question

17. Three alarm clocks ring their alarms at regular intervals of 20 min, 25 min and 30 min respectively. If they first beep together at 12 noon, at what time will they beep again for the first time? (b) 4:30 pm (a) 4:00 pm (d) 5:30 pm (c) 5:00 pm​

Answer 1

Answer:

(c)

Explanation:

We should find the LCM of the three alarm clocks,

20=2*2*5=2^2*5

25=5*5=5^2

30=2*3*5

LCM(20,25,30)=2^2*5^2*3=300min=5hrs

(c) 5:00pm