Numbering the pages of a book used 189 digits. How many pages does it have?
Hint: Pages 1-9 use 9 digits.
99 pages.
Pages 1-9 use 9 digits, leaving 180. Two-digit pages use 2 digits each, so 180 ÷ 2 = 90 more pages. 9 + 90 = 99.
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