The probability that it will rain today is 0.5. The probability that it will rain tomorrow is 0.6. The probability that it will rain either today or tomorrow is 0.7. What is the probability that it will rain today and tomorrow?
(A) 0.3
(B) 0.25
(C) 0.35
(D) 0.4
Answer: (D)
Explanation: Let A is the event that it will rain today and B is the event that it will rain tomorrow.
probability (A intersection B) = probability ( A ) + probability (B) - probability (A union B). probability (A intersection B) = 0.5 + 0.6 - 0.7 = 0.4