This question is incomplete because it was not written properly
Complete Question
A teacher gave his class two quizzes. 80% of the class passed the first quiz, but only 60% of the class passed both quizzes. What percent of those who passed the first one passed the second quiz? (2 points)
a) 20%
b) 40%
c) 60%
d) 75%
Answer:
d) 75%
Explanation:
We would be solving this question using conditional probability.
Let us represent the percentage of those who passed the first quiz as A = 80%
and
Those who passed the first quiz as B = unknown
Those who passed the first and second quiz as A and B = 60%
The formula for conditional probability is given as
P(B|A) = P(A and B) / P(A)
Where,
P(B|A) = the percent of those who passed the first one passed the second
Hence,
P(B|A) = 60/80
= 0.75
In percent form, 0.75 × 100 = 75%
Therefore, from the calculations above, 75% of those who passed the first quiz to also passed the second quiz.