एक कक्षा में 18 लड़के बहुत लम्बे हैं। यदि ये लड़के, लड़कों की कुल संख्या के तीन-चौथाई हैं और लड़कों की संख्या कक्षा के छात्रों की कुल संख्या की दो-तिहाई है, तो कक्षा में लड़कियों की संख्या क्या है ?
Read this question in English
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?
(a) 6 · (b) 12 · (c) 18 · (d) 21
उत्तर और व्याख्या · explanation in English
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). ·