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 find out when the traffic lights will change simultaneously again after 7 a.m., we need to calculate the Least Common Multiple (LCM) of the three time intervals: 48 seconds, 72 seconds, and 108 seconds.

### Step-by-Step Solution:

**Step 1: Prime Factorization of Each Number**
- 48 = 2 × 2 × 2 × 2 × 3 = \(2^4 \times 3^1\)
- 72 = 2 × 2 × 2 × 3 × 3 = \(2^3 \times 3^2\)
- 108 = 2 × 2 × 3 × 3 × 3 = \(2^2 \times 3^3\)
...