Sixty percent of the students in class are boys. If 12 of the students in the class are girls, what is the total number of students in the class?

So 60% of the class are boys, but we're given the number of girl students. We know that the remaining 40% of the class are girls, which equals 12 students. To find out the total number of students in the class we can divide the number we're given into 10%, which we can then multiply to give 100%.

So 40% of the class equals 12 students, we divide by 4 to give 10%, so 12 : 4 = 3. So 10% of the total class is 3 students, we times by 10 to find 100% of the class, so 3 x 10 = 30 students.