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# Math

## Understanding Sets and Set Notations

##### Example: A is the set of odd numbers less than or equal to 19 and B is the set of multiples of 3 less than 15. Write down the elements of A and B and find their union.  ##### The union of these sets is a set than contains all the elements of A and B. If an element belongs to both A and B, we do NOT write it twice in the union set. ##### Example:Find the intersection of the following sets:  ##### The intersection of the above two sets is a set of the elements that are in both A and B: ##### Example: Find the complement of A:  .

##### In order to find the complement of A, we have to subtract the elements of A from the universal set. ##### Example: Consider the universal set , and and Represent the sets in a Venn diagram. ##### Example: Show the following sets on a Venn diagram.    ##### An empty set is a set that includes no elements. We use Ø to represent an empty set. ##### Example: Is A a subset of B?  