Worked solution
Exclude a digit using arithmetic sums
Find the sum of all positive integers less than which do not contain the digit .
CJC · Discussion · Question 3
Answer
.
Subtract the two excluded arithmetic progressions
The total . The integers sum to . The integers sum to .
How did this part go?
Correct the double subtraction
belongs to both excluded groups. Add it back once: .
How did this part go?
Common mistakes
The overlap 33 must be subtracted only once.