What is the sum of all digits which appear in all the integers from 10 to 100?

Answer: (b) 856

From 10 to 99, each tens digit 1 to 9 appears 10 times (sum 450) and each units digit 0 to 9 appears 9 times (sum 405), which gives 855. The number 100 adds 1 more, so the total is 856.

1. Tens digits in 10–99: each of 1 to 9 appears 10 times → 10 × 45 = 450.
2. Units digits in 10–99: each of 0 to 9 appears 9 times (once in every ten) → 9 × 45 = 405.
3. Sum for 10–99 = 450 + 405 = 855.
4. Add the digits of 100: 1 + 0 + 0 = 1. Total = 856.

Remember · For digit-sum totals, count how often each digit appears in each place, and do not forget the end-points (here, 100).

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). · Report an error