2019 CSAT, all questions
UPSC Prelims 2019 · CSAT
Question 54: Logical Reasoning and Mental Ability
Consider the following sequence that follows some arrangement : c_accaa_aa_bc_b
The letters that appear in the gaps are
aabba
bcbbb
cbbbb
dcccc
AnswerUPSC’s answer is (b).
With the gaps filled by c, b, b, b the string reads cca | ccaab | aabbc | bb. It is built from five-letter blocks of the form xxyyz in which the letters rotate each time: bbcca, ccaab, aabbc, bbcca, with the first block cut off at the start. Each gap must be filled so that these blocks form, which gives c, b, b, b.
Why each option is right or wrong
- (a) Wrong: an a in the first gap breaks the opening cca.
- (b) Right: gives cca, ccaab, aabbc, bb.
- (c) Wrong: a b in the first gap gives cba, which breaks the opening cca.
- (d) Wrong: a c in the second gap gives ccaac, which breaks the block ccaab.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2019, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.