2020 CSAT, all questions
UPSC Prelims 2020 · CSAT
Question 15: Logical Reasoning and Mental Ability
Consider the following arrangement that has some missing letters : abab_b_bcb_dcdcded_d The missing letters which complete the arrangement are
aa, b, c, d
ba, b, d, e
ca, c, c, e
db, c, d, e
AnswerUPSC’s answer is (c).
Split the string into blocks of five letters. Each block alternates two letters, and the pair moves one step along the alphabet each time: ababa, bcbcb, cdcdc, deded. Matching this to the given string, the blanks are a, c, c and e in order. Remember: when a letter series looks irregular, try regrouping it into equal blocks.
Why each option is right or wrong
- (a) a, b, c, d: the first gap needs a, but the second needs c, not b.
- (b) a, b, d, e: the second gap must be c to make bcbcb.
- (c) Right: a, c, c, e complete ababa bcbcb cdcdc deded.
- (d) b, c, d, e: the first gap must be a, not b.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2020, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.