Thread: set theory question - how to handle duplicates?

In my very basic learning of set theory I have seen eg set A {1,2,3,4,5} and set B {2,3,5} for example and then I can work out A union B and A intersect B etc.

But in these cases there have been no duplicated integers. Is it possible to have duplicates in a single set? Or is that simply not allowed?

Could you for example have set A {1,1,1,1,2} and set B {1,2,2,2,2} ?

In which case what is the union and intersect?

Originally Posted by angypangy

Could you for example have set A {1,1,1,1,2} and set B {1,2,2,2,2} ?

In terms of true set theory, you have only one set there.
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In listing the elements of a set, each element is listed only once.