A pattern formed by two characters a and b is repeated more than once in the following string:
× b × a × a × × a × a × bab
What is × × in the 7th and 8th positions from the left in the above string?
Answer & explanation
Answer: (d) bb
The string has 15 places, so the repeating block has length 3 or 5. Length 3 clashes (place 2 is b but place 11 is a); length 5 fits every known letter and gives the block 'abbab', so places 7 and 8 are b and b.
- Number the 15 places: 1 ×, 2 b, 3 ×, 4 a, 5 ×, 6 a, 7 ×, 8 ×, 9 a, 10 ×, 11 a, 12 ×, 13 b, 14 a, 15 b.
- Block length 3 fails: places 2 and 11 should match but are b and a.
- Block length 5: places 1, 6, 11 → a; 2, 7, 12 → b; 3, 8, 13 → b; 4, 9, 14 → a; 5, 10, 15 → b.
- Block = abbab, repeated three times: abbab abbab abbab.
- Places 7 and 8 = 2nd and 3rd letters of the block = b, b.
Remember · For a repeated pattern, try block lengths that divide the string length; letters one block apart must match.
Question and answer: UPSC's provisional GS Paper II (2026, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·