10 से 100 तक लिखे जाने वाले सभी पूर्णांकों में आने वाले सभी अंकों का योगफल क्या है ?
Read this question in English
What is the sum of all digits which appear in all the integers from 10 to 100?
(a) 855 · (b) 856 · (c) 910 · (d) 911
उत्तर और व्याख्या · explanation in English
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.
- Tens digits in 10–99: each of 1 to 9 appears 10 times → 10 × 45 = 450.
- Units digits in 10–99: each of 0 to 9 appears 9 times (once in every ten) → 9 × 45 = 405.
- Sum for 10–99 = 450 + 405 = 855.
- 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). ·