If it takes 825 to number a book starting from page 1, how many pages are in the book?

Question

Pretty self explanatory :)

Answer 1

If you mean 825 digits...

pages 1-9 uses 9 digits

pages 10-99 uses 180 digits (90 2-digit pages)

pages 100-199 uses 300 digits (100 3-digit pages)

pages 200-299 uses 300 digits

so far you have used 300+300+180+9=789 digits

825-789=36 digits left

36/3=12 more 3-digit pages

300, 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 311

there are 311 pages in the book