I am compiling the new BrainBashers world almanac, and it now contains lots more pages.
I know that it takes 333 digits to print the page numbers in sequence.
How many numbered pages does the book have?
How many times does the number 3 appear?
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Hint
Think of the pages from 1 to 9, and then 10 to 99.
Answers
There are 147 pages.
The number 3 appears 35 times.
Answer #1
For pages 1 to 9, there are 9 pages, which is 9 digits.
For pages 10 to 99, there are 90 pages, which is 180 digits.
This is a total so far of 189, therefore we require another 333 − 189 = 144 digits, which is another 144 ÷ 3 = 48 pages.
Taking us to 9 + 90 + 48 = 147 pages in total.
Answer #2
From page 1 to 147 we have 15 pages that end in 3:
3, 13, 23, …, 143
We also have the ten pages that start with 30:
30, 31, 32, …, 39
Plus the ten pages that start with 130:
130, 131, 132, …, 139
For a total of 15 + 10 + 10 = 35 number 3's.
