Question

I want to know the number of proper subsets of this.
{1,3,5,7}. I found the subsets and I thought the proper subset of this is {1,3,5}. So How many proper subsets are there and list them please. I still don't understand.

Answer 1

"A PROPER subset is any subset of a set EXCEPT ITSELF.

So for instance, if you start with the set {Green Eggs, Ham, Cheese},
{Ham, Cheese} is a proper subset, but {Green Eggs, Ham, Cheese} is NOT
a proper subset."
copied and pasted from a website.... pretty interesting stuff
also
http://www.youtube.com/watch?v=fMW5QXMtD9I

Answer 2

{}
{1},{3},{5},{7}
{1,3},{3,5},{5,7}, {7,3},..... all pairs
{1,3,5},{3,5,7},......... all triplets

These are all proper subset of {1,3,5,7} except the set itself.

Answer 3

if the number of elements in a set is n, then the number of proper subsets is 2^n-1

Answer 4

Thank you everyone