Mathematics

Presenter Name : Mr. Pramote Phothisai

Topic : Sets

Subtopic : Union of sets

Objective

1. Explain meaning of the Union of sets.

2. Find the Union of two sets.

elements denoted diagram

covers

Union both represents

region

same

Interesting Words

Phrases referring to what we will talk about

The union of two sets

Is the set of all elements

The same elements of sets

The Venn diagram

That belongs to

Given the set

What is the elements of set A?

A = {2, 5, 8, 9, 11}

and B = {3, 5, 7, 8, 10}

Elements of set A are

What is the elements of set B?

Elements of set B are

2,

5,

8,

9,

11

3,

5,

7,

8,

10

Set A

What are the same elements of sets A and B?

= {2, 5, 8, 9, 11}

and B = {3, 5, 7, 8, 10}

The same elements of sets A and B are

5,

8

The union of two sets, A and B, denoted by

Union of sets

is the set of all elements

A Bthat belongs to A or B or both.

Example 1

(a) Find A B

Let A = {1, 3, 4, 9, 11}and B = {9, 11, 13}

Solution

(b) n(A B) =

(a) A B = {1,

3,

4,

9,

11,

13}

6

(b) Find n(A B)

Example 2

(a) Find P Q

Let P = {1, 3, 6, 8}

and Q = {2, 4, 6, 8, 10}

Solution (b) n(P Q) =

(a) P Q = {1, 2, 3, 4, 6, 8,

10}

7

(b) Find n(P Q)

The colored region in the Venn diagram belowrepresents A B. It covers both the regions representing A and B.

A B = {x : x A or x B}

Try It !

(a) Find M N

Let M = {a, b, d, e} and N = {d, e, k}

? ? ?

(b) Find n(M N)

Let M = {a, b, d, e} and N = {d, e, k}

Solution M N =

n(M N) =

{a, b, d, e, k}

5

OK. That’s it for today.

See you next time.

Thank you for your attention