2008 General Studies, all questions
UPSC Prelims 2008 · General Studies
Question 1: Logical Reasoning and Mental Ability
In the series AABABCABCDABCDE... which letter occupies the 100th position?
aH
bI
cJ
dK
AnswerThe answer is (b).
The series is built from growing blocks: A, AB, ABC, ABCD and so on, so block n has n letters and ends at position n(n+1)/2. Block 13 ends at position 91 (13 x 14 / 2). Block 14 therefore covers positions 92 to 105 and reads A to N in order. Position 100 is the 9th letter of that block, which is I.
Why each option is right or wrong
- (a) H is the 8th letter of block 14, at position 99.
- (b) I is the 9th letter of block 14, at position 100.
- (c) J is the 10th letter of block 14, at position 101.
- (d) K is the 11th letter of block 14, at position 102.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2008, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.