Consider two people being randomly selected. (For simplicity, ignore leap years.)

(a) What is the probability that two people have a birthday on the 9th of any month?
(b) What is the probability that two people have a birthday on the same day of the same month?

Step-by-step explanation:

Part (a) the probability that two people have a birthday on the 9th of any month.

Neglecting leap year, there are 365 days in a year.

There are 12 possible 9th in months that make a year calendar.

If two people have birthday on 9th; P(1st person) and P(2nd person).

Part (b) the probability that two people have a birthday on the same day of the same month

P(2 people selected have birthday on the same day of same month) + P(2 people selected not having birthday on  same day of same month) = 1

P(2 people selected not having birthday on  same day of same month):

P(2 people selected have birthday on the same day of same month)

step-by-step explanation: