Based on what I did for the other two can you figure out this one?
What is your answer?
Assume an office has two telephones (A and B) with separate lines and different telephone numbers. The probability that telephone A rings when the office is closed is .30. The probability that telephone B rings when the office is closed is .20.
What is the probability that telephone A or B rings when the office is closed?
2 answers
Either-or probabilities are found by adding the individual probabilities.