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Showing posts from July, 2026

Bird and Train Problem -- An Infinite Series and A Shortcut

  Some mathematical problems are beautiful not because of their answer, but because they can be approached in more than one way. The following puzzle is one such example. One method leads us through the fascinating world of infinite geometric series, while another arrives at the same answer through a simple observation. Exploring both approaches reminds us that mathematics is not just about reaching the destination—it is also about appreciating the different paths that lead there. Two trains are 100 km apart and moving toward each other, each at 50 km/h. A bird starts from the front of one train and flies toward the other at 100 km/h. When it reaches the second train, it instantly turns around and flies back toward the first train. It continues flying back and forth until the trains collide. How far does the bird fly? Many people try to calculate the distance of each individual trip, creating an infinite series. But this problem can be solved instantly by understanding it thoroughl...