It takes 26 seconds for a train to pass the 396 meter bridge and 18 seconds to pass the 252 meter tunnel. How long is the train's body?
The speed of the train is: (396-252) △ 26-18, = 144 △ 8, = 18 (M / s); the length of the train is: 18 × 18-252, = 324-252, = 72 (m); a: the body length of the train is 72 M
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