How do you do number 25? At the bottom.
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Answer-
The printer used 642 digits to print all the pages in the book.
Solution-
There are 250 pages numbered starting from 1 to 250.
The total number of digits would be the sum of digits of all single digits from 1 to 9, all double digits number from 10 to 99, and all triple digits number from 100 to 250.
There are 9 single digit numbers from 0 to 9, 90 double digit numbers from 10 to 99, and 151 triple digit numbers from 100 to 250.
So,
[tex]\text{Total digits}=(1\times 9)+(2\times 90)+(3\times 151)\\\\=9+180+453\\\\=642[/tex]
Therefore, the printer used 642 digits to print all the pages in the book.