So we DON"T want a selection of the type
PPP
TTT
SSS
Without any restrictions, number of selections
= C(14,3) = 364
Number choosing PPP = C(6,3) = 20
number choosing TTT = C(3,3) = 1
number choosing SSS = C(5,3) = 10
So we have to exclude (20+1+10) or 31
number of choices as specified = 364-31 = 333
A student who wants to buy 3 CDs, but assume that there are 6 CDs featuring the piano, 3 CDs featuring the trumpet, and 5 CDs featuring the saxophone.
In how many ways can the selection be made if CD's featuring at least 2 different instruments are selected?
I got 243, but that is not right
1 answer
3 answers