Question

Workers have been down the street installing two blinking red lights in front of the fire station. The two lights are always turned on at the same time. Both lights blink as they are turned on. One lights blinks after every 8 seconds. The other light blinks every 22 seconds. After how many seconds will they blink together again?

Answer 1

After 88 seconds, they will blink together.

Explanation:

Time after which the first light blinks = 8 seconds

Time after which the second light blinks = 22 seconds

Initially, both the lights blink together.

To find:

The time at which they will blink together again.

Solution:

Let us have a look at the time after which each light will blink.

First light will blink after:

8 s, 16 s, 24 s, 32 s, 40 s, 48 s, 56 s, 64 s, 72 s, 80 s, 88 s, 96 s, 104 s, ......

Second light will blink after:

22 s, 44 s, 66 s, 88 s, 110 s, .....

It can be seen that common time is 88 second, at which the both will blink together.

So, the answer is 88 s.

This answer can also be computed by taking the LCM (Least Common Multiple) of both the numbers i.e. 8 and 22.

Using the factorization method:

`8=\underline{2}* 2* 2`

`22=\underline{2}* 11`

Common is 2.

Therefore the LCM will be:

`2* 2*2* 11 = \bold{88}`

So, the answer is 88 s.