Question

Find the number of digits required to write down the number of pages in a $300$ pages book.

Answer 1

For one digit number 1 to 9
$\to 1\times 9=9$
For two digit number 10 to 99
$\to 2\times 90=180$
For three digit number 100 to 300
$\to 3\times 201=603$
Hence, total number of required digits
$=9+180+603=792$