UPSC Prelims 2000 · General Studies
Question 139: Basic Numeracy
In a class there are 18 boys who are over 160 cm tall. If these boys constitute three fourths of the boys and the total number of boys is two third of the number of students in the class, then what is the number of girls in the class?
AnswerThe answer is (b).
Eighteen boys are three fourths of the boys, so the number of boys is 18 x 4/3 = 24. The boys are two thirds of the class, so the class has 24 x 3/2 = 36 students. The girls are 36 - 24 = 12. As a check, 24 boys is two thirds of 36, and 18 is three fourths of 24.
Why each option is right or wrong
- (a) 6 is one fourth of the boys, not the girls.
- (b) Right: 36 students - 24 boys = 12 girls.
- (c) 18 is the number of boys over 160 cm.
- (d) 24 is the number of boys.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2000, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.