Question

two lighthouses flash their lights every 20 seconds and 30 s respectively. given that they flashed together at 4.10 pm, when will they next flash together?

Please give answer​

Answer 1

Answer:

8:01

Step-by-step explanation:

Answer 2

The two lights will next flash together at 4:11 pm.

Given,

Two lighthouses flash their lights every 20 s and 30 s respectively.

They flashed together at 4:10 pm.

To find,

When will the lights next flash together?

Solution,

Here, we can see that two lights are given to flash every 20 and 30 seconds respectively.

For the first time, as given, they flashed together at 4:10 pm.

Now, to determine when or after how long will they flash together again, we need to know the Least Common Multiple or LCM of 20 and 30.

We can find out the LCM by listing the multiples of 20 and 30 as follows.

Multiples of:

• 20 = 20, 40, 60, 80, 100, ... and so on.

• 30 = 30, 60, 90, ... and so on.

From the above, we can see that the LCM is,

LCM (20, 30) = 60.

It means, the lights will flash together again after 60 seconds, or, we can say after 1 minute.

So, the lights will flash together at

= 4:10 pm + 1 minute = 4:11 pm.

Therefore, the two lights will next flash together at 4:11 pm.

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