Set Theory

Question 1

A is a subset of B (which can be also written as A c B) means:
-that set B is within A
or
-that set A is within B

Answer 1

-that set A is within B

Question 2

If set A is {1,2,3,4,5} and set B is {1,2,3,4,5,6,7},
which is true?
-A c B
-B c A
-the two sets are disjoint
-A' is the same as B

Answer 2

A c B (set A is a subset of B)

Question 3

If set A is {2, 3, 7} and set B is {1, 4, 8},
which is true?
-A c B
-B c A
-the two sets are disjoint
-A' is the same as B

Answer 3

the two sets are disjoint (no overlap)

Question 4

If the universal set of colours is yellow, blue, red and purple, and set A is {yellow, blue} and set B is {red, purple}, which is true?

• A c B
• B c A
• the two sets are disjoint
• A’ is the same as B

Answer 4

the two sets are disjoint and A’ is the same as B (all of the colours in the universal set that aren’t in A are in B).

Question 5

If set A is {1, 3, 5, 6} and set B is {3, 8, 9, 10} what is the intersection of A and B?

Answer 5

3 is the intersection of A and B (3 is in both sets)

Question 6

If set A is {1, 3, 5, 6} and set B is {3, 8, 9, 10} what is the union of A and B?

Answer 6

The union of A and B would be {1,3,5,6,8,9,10} (all of the numbers in A and B)

Question 7

What does A U B mean?

• the intersection of A and B
• the union of A and B

Answer 7

A U B means the union of set A and B (all of the items/numbers in set A and B)

Question 8

What does A ∩ B mean?

• the intersection of A and B
• the union of A and B

Answer 8

-the intersection of A and B (the items/numbers that overlap between set A and B)

Question 9

What does A’ mean?

Answer 9

A’ is the complement of set A (all the elements not in set A)

Question 10

{} means what?

• an empty set
• a set that hasn’t been finished

Answer 10

{} means an empty set (nothing in it)