1. 


Two sets in which the same elements are listed in different orders are the same. 
2. 


The same element can never appear twice in a set. 
3. 


The empty set is a subset of itself. 
4. 


If two sets are not equal, then one is a subset of the other. 
5. 


If (A B) = A, then (A B) = B. 
6. 


If (A B) = (A B), then A = B. 
7. 


(A B)' = (A' B'). 
8. 


The number of possible outcomes when five coins are tossed, and the list of heads and tails is noted, is 10. 
9. 


The number of possible outcomes when three dice are thrown, and the list of numbers is noted, is 216. 
10. 


There are 5! possible lists of five different names. 
11. 


There are 5! possible sets of five different names. 
12. 


There are more sets of 5 chosen from 7 than there are sets of 2 chosen from 7. 
13. 


The following counting procedure is valid in forming a threeletter sequence using the letters a, a, b. Step 1: Choose the first letter. Step 2: Choose the second letter. Step 3: Choose the third letter. 
14. 


The following counting procedure is valid in forming a threeletter sequence using the letters a, a, b. Step 1: Place the first a. Step 2: Place the second a. Step 3: Place the b. 
15. 


There are 10 people whose names begin with "A" and 12 people whose names begin with "O." Thus there are a total of 120 people whose names begin either with "A" or "O." 
16. 


There are 10 people whose names begin with "A" and 12 people whose names begin with "O." Thus there are a total of 22 people whose names begin either with "A" or "O." 
17. 


In a hand of poker, a pair of 10's is more likely to come up than a full house. 
18. 


The number of lists of r objects chosen from n is always divisible by r!. 
19. 


The number of sets of r objects chosen from n is always divisible by r!. 
20. 


In a group of 339 people, at least two of them have the same firstname and lastname initials, possibly switched (as in Constance Smith and Selwyn Crown). 