GWD1-7

memory

7

（E）

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?

A.      42

B.      70

C.      140

D.     165

E.      315

为什么选E

tiger1234

c(7, 1) = 7!/(1!*6!) ways to choose the math guy; c(10, 2) = 10!/(2!*8!) to choose the other two dudes, so the total number of ways to choose these 3 ppl is: c(7, 1)*c(10, 2) = 315...