→ hhhtsai:希望能簡單說明一下理由~~感謝218.187.240.201 07/22
Two trains, each having a speed of 30km/h, are headed at each other on
the same straight track. A bird that can fly 60km/h flies off the front
of one train when they are 60km apart and heads dircetly back the other
train. On reaching the other train it flies dircetly back to the first
train, and so forth.
How many trips can the bird make from one train to the other before they
crash?
感謝~~
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