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?

Explanation

To solve the problem of when the traffic lights will change simultaneously again, we need to find the least common multiple (LCM) of the three time intervals: 48 seconds, 72 seconds, and 108 seconds. Here’s how we can do it step by step:

### Step 1: Find the prime factorization of each number.
- **48**:
- 48 = 2 × 24
- 24 = 2 × 12
- 12 = 2 × 6
- 6 = 2 × 3
...