A certain university will select 1 of 7 candidates eligible to fill a position in the mathematics department and 2 of 10 candidates eligible to fill 2 identical positions in the computer science department. If none of the candidates is eligible for a position in both departments, how many different sets of 3 candidates are there to fill the 3 positions?
42
70
140
165
315
发现这种选人的都是用乘法,比如A组8人里选2个 B组3人里选2个,就是 C(8,2)* C*(3,2)
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