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# The traffic lights at three different road crossings change after every 48 seconds, 72 seconds and 108 seconds respectively. If they change simultaneously at 7 a.m., at what time will they change simultaneously again?

**Solution:**

We will be using the concept of LCM(Least Common Multiple) to solve this.

To proceed with the given problem, we need to find the LCM of 48, 72, and 108.

Therefore LCM of 48, 72 and 108 = 2 × 2 × 2 × 2 × 3 × 3 × 3 = 432

Hence, after every 432 seconds, the light will change simultaneously.

Thus, the required time is 432 seconds which can be converted into minutes and seconds as 7 minutes 12 seconds past 7 a.m.

You can also use the LCM Calculator to solve this.

NCERT Solutions for Class 6 Maths Chapter 3 Exercise 3.7 Question 6

## The traffic lights at three different road crossings change after every 48 seconds, 72 seconds and 108 seconds respectively. If they change simultaneously at 7 a.m., at what time will they change simultaneously again?

**Summary:**

If the traffic lights at three different road crossings change after every 48 seconds, 72 seconds, and 108 seconds respectively, The required time is 432 seconds, and if they change simultaneously at 7 a.m., they will again change after 432 seconds or 7 minutes 12 seconds past 7 = (7:07:12)a.m.

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