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.

Question

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?

John · Answer

Based on what I did for the other two can you figure out this one? What is your answer?

PsyDAG · Answer

Either-or probabilities are found by adding the individual probabilities.