- To determine the length of the bridge, we first need to calculate the distance the train travels in 72 seconds.
- The speed of the train is 60 km/h.
- We convert the speed to meters per second: \(60 \times \frac{1000}{3600} \approx 16.67 \text{ m/s}\).
- The train crosses the entire length (train + bridge) in 72 seconds.
- Distance covered by the train in 72 seconds: \(16.67 \times 72 = 1200 \text{ meters}\).
- The train's length is 700 meters.
- Thus, the length of the bridge is \(1200 - 700 = 500 \text{ meters}\).
- Therefore, the correct option is **Option 4: 500 m**. ✔️

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