How many integers between 100 and 400 contain the digit 2 (what steps do I take to solve)?

1 Answer

• Well I would break it into groups.

  From 200 - 299,

  All numbers have a 2 so that is 100 integers.

  From 100 - 199,

  You have a 2 in 102, 112, ... 192, (not including 122) ... etc. It occurs 9 times.

  You have 10 2s from 120 to 129.

  Thats a total of 19 2s from 100 - 199

  The above is true for 300-399, 19 2s

  Obvious 400 has no 2s.

  So you have 100 + 19 + 19 = 138 2s