If 7 ⊕ 9 ⊕ 10 = 8, 9 ⊕ 11 ⊕ 30 = 5, 11 ⊕ 17 ⊕ 21 = 13, what is the value of 23 ⊕ 4 ⊕ 15?
Answer & explanation
Answer: (a) 6
Add the three numbers and then add the digits of the total: 26 → 8, 50 → 5, 49 → 13. For 23, 4 and 15 the total is 42, and 4 + 2 = 6.
- 7 ⊕ 9 ⊕ 10: 7 + 9 + 10 = 26, and 2 + 6 = 8 (fits).
- 9 ⊕ 11 ⊕ 30: 9 + 11 + 30 = 50, and 5 + 0 = 5 (fits).
- 11 ⊕ 17 ⊕ 21: 11 + 17 + 21 = 49, and 4 + 9 = 13 (fits).
- 23 ⊕ 4 ⊕ 15: 23 + 4 + 15 = 42, and 4 + 2 = 6.
Remember · For invented operators, test simple rules — sums, products, digit sums — on every given case and accept only one that fits all.
Question and answer: UPSC's official GS Paper II (2023, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·