9, 19, 29, 39, 49, 59, 69, 79, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99
=20
Chat with our AI personalities
Eleven.
11 with 1 remaining 100 - 1 = 99 = 9 x 11
111 of them with a remainder of 1
Well there will be 1 nine for all the 9s in the units column (9, 19, 29 etc.), and 1 nine for all the numbers with 9 in the tens column (90, 91, 92 etc.). So the answer is 20.
There are: 640/9 = 71 with a remainder of 1