Following is a matrix of certain entries. The entries follow a certain trend row-wise. Choose the missing entry (?) accordingly.
| 7B | 10A | 3C |
| 3C | 9B | 6A |
| 10A | 13C | ? |
Answer & explanation
Answer: (c) 3B
In each row the third number is the second minus the first, and the letters A, B and C each appear once. Row 3 therefore needs 13 − 10 = 3 with the letter B: 3B.
- Numbers, row 1: 10 − 7 = 3; row 2: 9 − 3 = 6 — the third number is the second minus the first.
- Row 3: 13 − 10 = 3.
- Letters: each row uses A, B and C once; row 3 already has A and C, so it needs B.
- The missing entry is 3B.
Remember · In matrix puzzles treat numbers and letters as separate patterns, and check each rule against every row.
Question and answer: UPSC's official GS Paper II (2021, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 1 Oct 2026 (how we verify). ·