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 quiz also passed the second quiz?

60/80 = 75%

To find the percentage of students who passed both quizzes out of those who passed the first quiz, we need to use the concept of conditional probability.

Step 1: Find out the percentage of the class that passed only the first quiz.
The percentage of the class that passed only the first quiz can be calculated by subtracting the percentage of students who passed both quizzes from the percentage of students who passed the first quiz.

Percentage passed only the first quiz = Percentage passed first quiz - Percentage passed both quizzes

Given that 80% of the class passed the first quiz and 60% of the class passed both quizzes:
Percentage passed only the first quiz = 80% - 60% = 20%

Step 2: Find the percentage of those who passed the first quiz and also passed the second quiz.
The percentage of students who passed both quizzes out of those who passed the first quiz can be calculated by dividing the number of students who passed both quizzes by the number of students who passed the first quiz and multiplying by 100.

Percentage of those who passed both quizzes out of those who passed the first quiz = (Number passed both quizzes / Number passed first quiz) × 100

Given that 20% of the class passed only the first quiz, the number of students who passed the first quiz is 80 - 20 = 60.
Therefore, the percentage of those who passed the first quiz and also passed the second quiz is (60 / 80) × 100 = 75%.

So, 75% of those who passed the first quiz also passed the second quiz.

To find the percent of those who passed the first quiz and also passed the second quiz, we need to divide the number of students who passed both quizzes by the number of students who passed the first quiz and then multiply by 100 to get the percentage.

Step 1: Let's assume the total number of students in the class is 100, for simplicity.

Step 2: If 80% of the class passed the first quiz, then the number of students who passed the first quiz is: 0.8 * 100 = 80.

Step 3: If 60% of the class passed both quizzes, then the number of students who passed both quizzes is: 0.6 * 100 = 60.

Step 4: Now, to find the percent of those who passed the first quiz and also passed the second quiz, we divide the number of students who passed both quizzes (60) by the number of students who passed the first quiz (80), and then multiply by 100:

Percentage = (Number of students who passed both quizzes / Number of students who passed the first quiz) * 100
= (60 / 80) * 100
= 0.75 * 100
= 75%.

Therefore, 75% of those who passed the first quiz also passed the second quiz.