Given the small numbers in the answer choices, another viable approach is to simply list the allowable outcomes:nafiul9090 wrote:how many two element subsets of (1,2,3,4) are there that do not contain the pair of elements 2 and 4
one
two
three
four
five
I think you are answering the question - "How many 2-sets that do not contain either 2 or 4?"coolhabhi wrote:IMO two.
take a list of all the two element subsets of (1,2,3,4). We have
(1,2) (1,3) (1,4)
(2,1) (2,3) (2,4)
(3,1) (3,2) (3,4)
(4,1) (4,2) (4,3)
An other way to look at it is :
If two elements are removed then the set will be (1,3).
So we can get on 2! subsets. that is 2.
BTW what is the OA?
