Events A and B are mutually exclusive. Suppose event A occurs with probability $0.19$ and event B occurs with probability $0.72$. If A does not occur, what is the probability that B does not occur? Round your answer to at least two decimal places.

My answer is $0.09/0.81=0.11$

Is my answer correct?

  • 2
    $\begingroup$ I don't understand the down vote. The OP stated his question clearly and showed his work. What more do you want? $\endgroup$
    – saulspatz
    Apr 10, 2018 at 6:17
  • $\begingroup$ Looks right to me. $\endgroup$
    – saulspatz
    Apr 10, 2018 at 6:19
  • 1
    $\begingroup$ Well, indeed, while Jake didn't show all the work, the numbers are certainly correct. It's not too bad as questions go. (Better than many we see.) $\endgroup$ Apr 10, 2018 at 6:26

1 Answer 1


Yes.   But you really should show your work instead of just magic numbers. $$\begin{split}\mathsf P(B'\mid A')&=\dfrac{\mathsf P(B'\cap A')}{\mathsf P(A')}\\[2ex] &=\dfrac{1-\mathsf P(B)-\mathsf P(A)\require{cancel}\cancelto 0{+~\mathsf P(A\cap B)}}{1-\mathsf P(A)}\\[2ex] &= \dfrac{0.09}{0.81}\end{split}$$


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .