Multiplication Rule 2: When two events, A and B, are dependent, the probability of both occurring is:
Problem: A math teacher gave her class two tests. 25% of the class passed both tests and 42% of the class passed the first test. What is the probability that those who passed the first test also passed the second test?
Solution: P (First and Second) = P(First)xP (Second│First).
P (Second│First) = P (First and Second)/ P (First)
= 0.25 / 0.42 = 0.60 = 60%
Example : The probability that it is Friday and that a student is absent is 0.03. Since there are 5 school days in a week, the probability that it is Friday is 0.2. What is the probability that a student is absent given that today is Friday?
Solution:P(Friday and Absent)= P (Friday) x P (Absent│Friday)
P (Absent│Friday) = P (Friday and Absent)/ P (Friday)
Solution:
= 0.03 /0.2 = 0.15 = 15%
