UPSC Prelims 2021 · CSAT
Question 40: Logical Reasoning and Mental Ability
In the English alphabet, the first 4 letters are written in opposite order; and the next 4 letters are written in opposite order and so on; and at the end Y and Z are interchanged. Which will be the fourth letter to the right of the 13^th letter ?
AnswerUPSC’s answer is (b).
Write the alphabet in blocks of four, each reversed: DCBA HGFE LKJI PONM TSRQ XWVU, then Y and Z swapped to give ZY. The 13th letter is the first of the fourth block, P. The next letters to its right are O (14th), N (15th), M (16th) and T (17th). The fourth letter to the right of P is T. Remember: write out the full rearranged sequence with positions rather than counting in the original alphabet.
Why each option is right or wrong
- (a) N is the second letter to the right of P.
- (b) Right: positions 14 to 17 are O, N, M, T, so the fourth to the right of P is T.
- (c) H is in the second block, to the left of the 13th letter.
- (d) I is in the third block, to the left of the 13th letter.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2021, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.