<p>How many numbers between 1-99 contain the digit 9?</p>
<p>If you guessed 10, you're wrong! The correct response is 19. =
9,19,29,39,49,59,69,79,89,90,91,92,93,94,95,96,97,98,99 </p>
<p>Most forget about the 90-98 part</p>
<p>I guessed 20 just off the top of my head heh =/ I was only off by one though!</p>
<p>There's a simple way to do this:</p>
<p>To calculate the numbers that don't contain a 9. There are 9 possible digits for the first digit and 9 possible for the second, so 9*9=81. However, since 0 isn't one of the possibilities, subtract 1. Therefore, 99-80=19.</p>
<p>That wasn't hard at all.</p>