20 students are in a classroom. if students leave randomly, the probability that the first student to leave the classroom is a girl is 3/5. How many girls are there?

3/5 * 20 = ?

12

120 To find out how many girls are in the classroom, we need to use some probability concepts. Let's assume that there are x girls in the classroom.

The probability that the first student to leave the classroom is a girl can be thought of as the probability of selecting a girl from the total number of students (x girls and 20 - x boys) in the classroom.

The total number of ways to select the first student to leave the classroom is 20 since any student can be the first to leave.

The total number of ways to select a girl from the x girls is x.

Therefore, the probability of selecting a girl as the first student to leave is x/20.

According to the given information, this probability is 3/5. So we can set up an equation:

x/20 = 3/5

To solve for x, we can cross multiply:

5x = 20 * 3

5x = 60

x = 60/5

x = 12

So, there are 12 girls in the classroom.