Question

A light blinks after every 3 seconds, another light blinks after every 5 seconds. How many times do they blink together in half an hour.

Answer 1

lcm of 3 and 5 is 15
seconds in half an hour = 1800
times in 30 mins= 1800÷15=120

Answer 2

Answer:

120 times do they blink together in half an hour.

Step-by-step explanation:

Given : A light blinks after every 3 seconds, another light blinks after every 5 seconds.

To find : How many times do they blink together in half an hour.

Solution :

According to question,

We take the LCM of 3 and 5

i.e, LCM(3,5)=15

1 hour = 60 minutes = 3600 seconds

$\frac{1}{2} hr=\frac{3600}{2}s$

$\frac{1}{2} hr=1800s$

Times in 30 mins= $\frac{1800}{15}=120$

Therefore, 120 times do they blink together in half an hour.