Question

Eric’s notebook has 30 pages. He wants to write a number on each page. How many digits will he write when he numbers all the pages in the notebook?

Answer 1

Hint: Since Erics’ notebook has 30 pages, you need to split them into two parts. The first 10 9 pages contain only one digit for each page so you get a total 9 digits. The next 10 to 30 pages contains 2 digits each page. Therefore, multiply two to the number of pages between 10 and 30 to get the number of digits. Then add this to the 9 digits to get the final answer.

Complete step by step solution:

Here is the step wise solution. In this, the first step is to split the thirty page to 1 to 9 and then 10 to 30 since in page 1 to 9 he can write one digit and in pages 10 to 30 he can write 2 digits each page.
First for page one to 9 he can write a total of
$\Rightarrow 9 \times 1 = 9$
Here 9 is for 9 pages and 1 is for each digit one page. Therefore, for pages 1 to 9 we have 9 digits.
For the pages 10 to 30 he can write a total of
$\Rightarrow 21 \times 2 = 42$
Here 21 is for 21 pages between 20 and 30 pages and 2 is for two digit one page. Therefore, for pages 20 to 30 we have 42 digits.
 Therefore, total number of digits are $ 42+9 = 51$

Therefore, The final for the question is 51 digits.

Note: Be careful to calculate the number of digits not the numbers, as for numbers you get a total of 30 numbers and for digits you get a total of 51 digits. Also don’t forget and calculate 2 digits each page even for pages 1 to 9 as you will get the wrong answer.