In a group of students, the ratio of girls to boys is 3 to 2. If there are 15 girls, how many total students are there?

The ratio of girls to boys is 3:5, or three to five. This means that for every 5 boys, there are 3 girls in the class. We can think of the boys as being in "groups" of 5. For every group of 5 boys, there will be a group of 3 girls. How many groups of 5 boys are in the classroom? There are 15 boys, which means there are 3 groups of 5 (3 times 5 equals 15). Since there are 3 girls for every 5 boys, this means there are also 3 groups of girls, but there are 3 girls in each group instead of 5. 3 times 3 equals 9, so there are 9 girls. Total students equals 15 plus 9, or 24. Another way of thinking about this is by cross multiplying. 3/5 = g/15 (make sure you keep the boys and girls in the same order. Girls are in the numerator, boys are in the denominator for both). When you cross multiple, you get 3 * 15 = 5*g. Solve for g, and you get g = (3 * 15) / 5, or 45 / 5, or 9. Add 9 to the 15 boys for the total, and you get 24.