Consider “words” consisting of any string of 5 upper case letters...
Consider “words” consisting of any string of 5 upper case letters fromthe first half of the usual alphabet: A,B,C,D,E,F,G,H,I,J,K,L,M.
(a) How many words contain at least one A?
If 13^5 = all words we can make (371,293)
12^5 = all words ex. A's (248,832)
== 122,461
(b) How many words contain exactly two A’s?
would this be: 13 x (12 choose 3) x (5 choose two) x 3! ?
Consider “words” consisting of any string of 5 upper case letters fromthe first half of the usual alphabet: A,B,C,D,E,F,G,H,I,J,K,L,M.
(a) How many words contain at least one A?
If 13^5 = all words we can make (371,293)
12^5 = all words ex. A's (248,832)
== 122,461
(b) How many words contain exactly two A’s?
would this be: 13 x (12 choose 3) x (5 choose two) x 3! ?