How many integers from 100 to 999 contain at least one 2 or at least one 5 as digits?
+605 We use complementary counting: what we don't want. How many options for the first digit? 1,3,4,6,7,8,9=7. Second? 0,1,3,4,6,7,8,9=8. Third? 0,1,3,4,6,7,8,9=8. So 7*8*8=448 in total. There are 900 total 3 digit numbers, so 900-448=452. Ans.
