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Union And Intersection

Unions

Unions are the act of combining 2 set together into a single set. Essentially you take all the elements from both sets and create a new set with all the elements from both. One thing to note is that if an element appears in both sets then you only list it once in the new set. The symbol for union is ∪ or basically a U.

Example:

A={4,6,12,65} B={6,15,42,87}

A Union B = {4,6,12,15,42,65,87} A ∪ B = {4,6,12,15,42,65,87}

As I mentioned even though 6 appears in both of the original sets it is only written once in the new set.

Intersections

Intersections are the second important operation you should know how to apply. This operation takes 2 sets and combines them into a new set that has only the elements that were in both sets. The symbol for Intersection is an upside down U or ∩

Example:

A={3,4,6,12,65} B={3,6,13,65,87}

A Intersect B = {3,6,65} A ∩ B = {3,6,65}

Practice Problems

A={2,5,6,8,10,23,67,88,101,134} B={1,6,7,10,34,67,76,96,101,155}

Write the set for A Union B.

A ∪ B = ?

Write the set for A Intersect B.

A ∩ B =?