Of the ten digits, 0 is the only one that is divisible by 9.
The least three-digit number that is divisible by both 5 and 9 is 135.
987
144 is divisible by 12 and 9.
999
225
900
180
900
3, 6, 9
100. The highest 3 digit number divisible by 9 is 999 (111 times). The highest 2 digit number divisible by 9 is 99 (11 times). The difference is 100.
135
If you multiply 2*9, you get 18. Multiply that by 10 to get a three digit number, and you get 180.