In a class, there are 18 very tall boys. If these constitute three-fourths of the boys and the total number of boys is two-thirds of the total number of students in the class, what is the number of girls in the class?
Answer & explanation
Answer: (b) 12
Eighteen is three-fourths of the boys, so there are 24 boys. They are two-thirds of the class, so the class has 36 students and 12 of them are girls.
- Boys = 18 ÷ 3/4 = 24.
- Class = 24 ÷ 2/3 = 36.
- Girls = 36 − 24 = 12.
Remember · Work back from the part to the whole one fraction at a time: whole = part ÷ fraction.
Question and answer: UPSC's official GS Paper II (2016, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·