Question

Number of 6 digit numbers where sum of digits is divisible by 5

Answer 1

You can say that in every consecutive 10 numbers where only the ones place is changing, there would be exactly 2 such numbers whose digits' sum is divisible by 5. I can have (100 - 109), (110 - 119) … (990 - 999) i.e. 90 such cases as there are 900 3 digit numbers.