In a class of 20 students, if 12 are girls, what is the probability that a student chosen at random is a boy?

• A. 12/20
• B. 8/20
• C. 1/2
• D. 4/20

Answer: (B)

To find the probability that a randomly chosen student is a boy, we first need to determine the number of boys in the class. Given that there are 20 students in total and 12 of them are girls, we calculate the number of boys by subtracting the number of girls from the total number of students:

Number of boys = Total students - Number of girls = 20 - 12 = 8 boys.

Probability is calculated as the number of favorable outcomes divided by the total number of possible outcomes. In this case, the favorable outcome is picking a boy, and the total possible outcomes is the total number of students:

Probability of choosing a boy = Number of boys / Total number of students = 8 / 20.

This fraction can also be simplified to 2 / 5, but when looking at the options, the correct way to express this probability in its original form is 8/20.

Therefore, the correct answer reflects the total number of boys over the total class size, making that option the correct choice.