In a class of 60 students, where the number of girls is twice that of boys, Kamal, a boy, ranked seventeenth from the top. If there are 9 girls ahead of Kamal, the number of boys in rank after him is :
- (a) 13
- (b) 12 ✓ UPSC's answer
- (c) 7
- (d) 3
Why the answer is (b)
• Total students are 60, with girls being twice the number of boys, so there are 20 boys and 40 girls.
• Kamal is ranked 17th from the top, meaning there are 16 students ahead of him.
• Since 9 of the students ahead of Kamal are girls, the remaining 7 students ahead of him must be boys (16 - 9 = 7).
• Including Kamal, there are 8 boys in the top 17 ranks (7 ahead + Kamal).
• The number of boys ranked after Kamal is the total number of boys minus the boys in the top 17 ranks: 20 - 8 = 12.
Why the other options are wrong
- (a) 13
- Option (a) is incorrect because it likely results from miscalculating the number of boys ahead of Kamal or subtracting incorrectly from the total.
- (c) 7
- Option (c) is incorrect because it confuses the number of boys ahead of Kamal (7) with the number of boys behind him.
- (d) 3
- Option (d) is incorrect because it does not account for the total number of boys in the class correctly relative to Kamal's position.
Asked in the CSAT Paper II of the UPSC Civil Services Preliminary Examination 2016, held on 7 August 2016. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.