In a code language ‘MATHEMATICS’ is written as ‘LBSIDNZUHDR’. How is ‘CHEMISTRY’ written in that code language?
Answer & explanation
Answer: (b) BIDNHTSSX
The code moves letters alternately one step back and one step forward (M→L, A→B, T→S, H→I …). Applied to CHEMISTRY, this gives BIDNHTSSX.
- MATHEMATICS → LBSIDNZUHDR: M−1 = L, A+1 = B, T−1 = S, H+1 = I, E−1 = D, M+1 = N, A−1 = Z … — alternately −1 and +1.
- CHEMISTRY: C−1 = B, H+1 = I, E−1 = D, M+1 = N, I−1 = H, S+1 = T, T−1 = S, R+1 = S, Y−1 = X.
- Code: BIDNHTSSX.
- Check: (c) BIDLHTSSX differs only in the 4th letter — M+1 is N, not L.
Remember · In letter codes, write the shift under each letter; alternating shifts (−1, +1) are common. Compare options only where they differ.
Question and answer: UPSC's official GS Paper II (2021, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·