How many of the natural numbers from 1 to 800 inclusive, contain the digit 6 at least once?
+128460 All the integers from 600 - 699 contain at least one 6 = 100 numbers
In every 100 except from 600 - 699 we will have
10 numbers containing at at least one 6 from _60 to _69 = 7 (10) = 70 numbers
9(7) = 63 more numbers that have an ending digit of 6
So
100 + 70 + 63 =
233 numbers contain at least one 6
