In a class of 24 students with the ratio of boys to girls 3:5, how many girls are there?

In a class of 24 students with the ratio of boys to girls 3:5, how many girls are there?

• A. 15
• B. 9
• C. 24
• D. 10

Answer: (A)

When a ratio is given, think in parts. The ratio of boys to girls is 3:5, so there are 3 parts boys and 5 parts girls, for a total of 3 + 5 = 8 parts. The class has 24 students, so each part represents 24 ÷ 8 = 3 students. The girls correspond to 5 parts, so there are 5 × 3 = 15 girls. Checking: boys would be 3 parts, or 9 students, and 9 + 15 = 24 with a 9:15 ratio simplifying to 3:5, which matches the given ratio. Therefore, there are 15 girls.

When a ratio is given, think in parts. The ratio of boys to girls is 3:5, so there are 3 parts boys and 5 parts girls, for a total of 3 + 5 = 8 parts. The class has 24 students, so each part represents 24 ÷ 8 = 3 students. The girls correspond to 5 parts, so there are 5 × 3 = 15 girls. Checking: boys would be 3 parts, or 9 students, and 9 + 15 = 24 with a 9:15 ratio simplifying to 3:5, which matches the given ratio. Therefore, there are 15 girls.