1. ## [SOLVED] Counting principles

I have had difficulty understanding this topic with Union and Mutually exclusive involved. Can anyone explain what is the N( X U Y) and the N ( X *upside down U* Y) is? the book is confusing me because they are using it interchangeably

Also I have a question on my hw (I will use the letter i for the upsidedown U)

Suppose two fair dice are rollled, Find N(X U Y) and N(X i Y)

X=the first die shows 6
Y=the sum of the dice is 10

2. Originally Posted by something3k
I have had difficulty understanding this topic with Union and Mutually exclusive involved. Can anyone explain what is the N( X U Y) and the N ( X *upside down U* Y) is? the book is confusing me because they are using it interchangeably

Also I have a question on my hw (I will use the letter i for the upsidedown U)

Suppose two fair dice are rollled, Find N(X U Y) and N(X i Y)

X=the first die shows 6
Y=the sum of the dice is 10
U means union, which means cases X OR Y is satisfied.
In your example, it means the first die is 6 or the sum of the dice is 10.
So X U Y will be (6, 1) (6, 2) (6, 3) (6, 4) (6, 5) (6, 6) (4, 6) (5, 5)
There are 8 cases. So N (X U Y) is 8.

inverted U means intersection, which means cases X AND Y are satisfied.
In your example, it means that the first die is 6 and the sum of the dice is 10.
So X intersect Y will be only (6, 4)
There is only 1 case. So N (X intersect Y) is 1.

Hope this helps.

3. yea i had to read that over like 5 times and other stuff but i think im getting it, thanks