# Thread: Intersection and Union problem

1. ## Intersection and Union problem

How do I do this? Freshman in need of serious help

A={3,6,7,12} B={1,3,5,7,15} C={6,7,11,15}
(A"union"B)"intersection"C

People please answer. I don't have the symbol for union and intersection on my laptop. That's why I put the words in parenthesis.

3. $\displaystyle A \cup B = \{1,3,5,6,7,12,15 \}$

$\displaystyle (A \cup B) \cap C = \{6,7,15 \}$

4. Originally Posted by tukeywilliams
$\displaystyle A \cup B = \{1,3,5,6,7,12,15 \}$

$\displaystyle (A \cup B) \cap C = \{6,7,15 \}$
Ok why did you get rid of the eleven. can you explain (so I can explain it in class)?

5. There's no $\displaystyle 11$ in $\displaystyle A \cup B$ but there is an $\displaystyle 11$ in $\displaystyle C$. So $\displaystyle A \cup B$ and $\displaystyle C$ do not share $\displaystyle 11$ as a common element (i.e. the intersection between these two sets does not contain $\displaystyle 11$).

There's no $\displaystyle 11$ in $\displaystyle A \cup B$ but there is an $\displaystyle 11$ in $\displaystyle C$. So $\displaystyle A \cup B$ and $\displaystyle C$ do not share $\displaystyle 11$ as a common element (i.e. the intersection between these two sets does not contain $\displaystyle 11$).