Explain me train problems consisting of speed, distance and time

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Welcome to train problems! These problems involve calculating relationships between speed, distance, and time. The fundamental formula is distance equals speed times time. We can rearrange this formula to solve for speed or time when needed. The first type of train problem involves a train crossing a point object like a pole or signal post. In this case, the distance covered by the train equals the length of the train itself. For example, if a 150 meter train crosses a pole at 60 kilometers per hour, we first convert the speed to meters per second, then calculate the time as distance divided by speed, which gives us 9 seconds. The second type involves a train crossing a platform or bridge. Here, the distance covered equals the train length plus the platform length. For example, a 120 meter train crossing a 180 meter platform at 72 kilometers per hour. The total distance is 300 meters, speed converts to 20 meters per second, giving us 15 seconds to completely cross the platform. The third type involves two trains crossing each other. The distance is the sum of both train lengths. For relative speed, if trains move in the same direction, we subtract speeds; if opposite, we add them. In our example, a 100 meter train at 60 kilometers per hour meets a 150 meter train at 40 kilometers per hour in opposite directions. Total distance is 250 meters, relative speed is 100 kilometers per hour, giving us 9 seconds for complete crossing. To summarize what we have learned about train problems: They all use the fundamental distance equals speed times time formula. For point objects, distance equals train length. For platforms, add platform length to train length. For two trains, use the sum of both lengths and calculate relative speed by adding speeds for opposite directions or subtracting for same direction.