Caribou Math Contest & Combinatorics

Question 5 of 18 (3 points)

Joyce sells comic books, adventure books, and mystery books at her book store. If a customer wants to select two books of different types, how many different combinations are there?

1. 3
2. 4
3. 5
4. 6
5. 7
6. 8
7. 9

Question 11 of 18 (4 points)

Using the letters A and B, one can form the following two-letter code words: AA, AB, BB, BA. How many different four-letter code words can be formed using the letters A, B, C, and D?

1. 16
2. 24
3. 64
4. 120
5. 204
6. 256
7. 308

Combinatorics
Combinatorics & Permutations.....
Open the above links and learn about combinatorics.