Solution: Solve according to the properties of classical concepts , permutations , combinations and probability .

　　Number the parts from to In test , rivets are installed on each part . Let represent the event " the strength of the i th part is too weak " . If rivets with too weak strength are installed on the i-th component at the same time b occur. Choose any rivets from and install them on the i th component. There are ways to choose them. However, there are only rivets that are too weak. They are all installed on the -th component. There are only ways to choose them, so

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　　Since is mutually exclusive , according to the property of probability 2, the probability that one of the components is too weak is

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