A middle school principal has 80 keys on her key chain to distribute to staff on the first day of school. Of these
80 keys, 60 open classroom doors, 40 open the door to the teachers' lounge, and 30 open classroom doors and
the teachers' lounge. Using this information, answer each of the following questions.
Let C be the event that a randomly selected key opens a classroom and T be the event that a randomly
selected key opens the teachers' lounge.
What is P(C), the probability that a key opens a classroom?
What is P(T), the probability that a key opens the teachers' lounge?
What is P(C and T'), the probability that a key opens a classroom and the teachers' lounge?
What is P(C or T), the probability that a key opens a classroom or the teachers' lounge?
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