Consider the following arrangement that has some missing letters : abab_b_bcb_dcdcded_d The missing letters which complete the arrangement are
- (a) a, b, c, d
- (b) a, b, d, e
- (c) a, c, c, e ✓ UPSC's answer
- (d) b, c, d, e
Why the answer is (c)
• The sequence is composed of four distinct repeating patterns: 'abab', 'bcb', 'dcdcd', and 'ded'.
• The first segment 'abab' is followed by a missing letter, which must be 'a' to start the next pattern or complete the current block structure.
• The second segment is 'b_bcb'. To form a symmetric or repeating pattern like 'bbcb' or similar, the missing letter is 'c', resulting in 'bcbcb' or fitting the 'c' from the next group.
• The third segment is 'dcdcded_d'. The pattern 'dcdcd' is followed by 'ed', and the final missing letter completes the 'ded' pattern, which is 'e'.
• Analyzing the specific gaps: The first gap after 'abab' is 'a'. The second gap in 'b_bcb' is 'c' (forming 'bcbcb' or similar logic). The third gap in 'dcdcded_d' is 'c' (completing 'dcdcdedc' or similar). The final gap is 'e'.
• Therefore, the missing letters are a, c, c, e, which corresponds to option (c).
Why the other options are wrong
- (a) a, b, c, d
- Option (a) suggests the second missing letter is 'b', but the pattern requires 'c' to maintain the sequence logic.
- (b) a, b, d, e
- Option (b) suggests the third missing letter is 'd', but the pattern requires 'c' to complete the specific sub-sequence.
- (d) b, c, d, e
- Option (d) suggests the first missing letter is 'b', but the sequence starts with 'a' to continue the 'abab' pattern.
Asked in the CSAT Paper II of the UPSC Civil Services Preliminary Examination 2020, held on 4 October 2020. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.