Question with intersects and complements.

1. Sep 26, 2008

Shawj02

Ok, first post.
So I have this question, which goes something like this...
Given
P(A)=0.3, P(B)=0.3, P(C)=0.7
P(AnB^c)=0.2, P(AnC^c)=0.2, P(AnBnC)=0

Find P((AnB)U(AnC))

(Where; n =intersect, U union, ^c = complement.)

Personally my thoughts are..
P(AnBnC)=0. Therefore mutually exclusive.

And then Because probability cannot be negative. I think that leads to P(AnB)=0,P(AnC)=0 & p(BnC)=0.
Which couldnt be right, As that would give P((AnB)U(AnC)) = 0U0 = 0.

My major concern is how do I change P(AnC^c) & P(AnB^c) to something useful!

Thanks!

2. Sep 26, 2008

Shawj02

Ive got
P(A)- P(AnB^c) + P(A)- P(AnC^c)= P((AnB)U(AnC))

Anyone want to double check me?

3. Sep 26, 2008

mathman

It's correct. Do you understand how? Also you obviously can get a number from it.

4. Sep 26, 2008

Shawj02

Awesome. Yeah, I understand how. Just had a block a guess.
Thanks.