Another GRE study question
Let A, B, C, and D be events for which P(A or B) = 0.6, P(A) = 0.2, P(C or D) = 0.6,and P(C) = 0.5. The events A and B are mutually exclusive, and the events C and D are independent.
Part (a) asks find P(B), which is
$P(A \cup B) = P(A) + P(B)$ $0.6 = 0.2 + P(B)$ $P(B) = 0.4$
But part (b) asks find P(D), and when I try, my answer is $0.1$
$P(D) = P(C\cup D) - P(C) = 0.6 - 0.5 = 0.1$
This is incorrect. According to the study guide, answer is $0.2$
Please explain