Explanation:

- Two trains are moving in the same direction with speeds of 50 km/h and 30 km/h.

- The relative speed is the difference in their speeds: \(50 - 30 = 20 \text{ km/h}\).

- Convert the relative speed to meters per second: \((20 \times \frac{1000}{3600} \approx 5.56 \text{ m/s})\).

- Total length to cross is 450 m + 550 m = 1000 m.

- Time taken to cross each other = \(\frac{1000}{5.56} \approx 180 \text{ seconds}\).

- Convert seconds to minutes: 180 seconds = 3 minutes.

- Correct Answer: Option 1, 3 minutes