# Math Help - intersection and union

1. ## intersection and union

Can anyone help me with intersection and union? I do not understand it, and this paper is due in the am

2. Originally Posted by shawnialayne
Can anyone help me with intersection and union? I do not understand it, and this paper is due in the am
You're a little vague. What do you need to know about them? What course are you taking, etc.

-Dan

3. Originally Posted by shawnialayne
Can anyone help me with intersection and union? I do not understand it, and this paper is due in the am
you need to be more specific as to what you want. have you tried google or wikipedia?

basically, the intersection of two or more sets is the set of elements that are common to each and every set.

the union is the set of all elements in all the sets, whether they are in common or not.

example: let $A = \{ 1,2,3,4,5,6 \}$ and $B = \{ 1,3,5,7,9 \}$

then the intersection is: $A \cap B = \{ 1,3,5 \}$, since those are the elements the sets have in common

and the union is: $A \cup B = \{ 1,2,3,4,5,6,7,9 \}$

If we had a third set, $C = \{ 1 \}$

then $A \cap B \cap C = \{ 1 \}$

and $A \cup B \cup C = \{ 1,2,3,4,5,6,7,9 \}$