What value of p makes A and B mutually exclusive events?

[das1]

Here's another probability question that's confusing me, any help would be appreciated!

Let A and B be two events with P(A) = 0.4, P(B) = p, and P(A or B) = 0.8. For what value of p will A and B be mutually exclusive? (Round to four decimal places as appropriate.)

 

[chisigma]

Here's another probability question that's confusing me, any help would be appreciated!

Let A and B be two events with P(A) = 0.4, P(B) = p, and P(A or B) = 0.8. For what value of p will A and B be mutually exclusive? (Round to four decimal places as appropriate.)

Two events A and B are mutually exclusive if P (A & B)=0. In general is P(A or B) = P(A) + P(B) - P(A & B), so that...

Kind regards

$\chi$ $\sigma$

 

[das1]

That was the formula I wanted, thanks!