I am trying to find all $2$ digit numbers that are divisible by $5$. So, if we put the $0$ at the last position - _$0$, we have $V_9^1=9$ options for the first digit. If we put $5$ at the last position - _$5$, we have $V_9^1=9$, but this includes $05$. The total number is: $2V_9^1-1=17.$ Aren't they $18$?
2026-04-02 05:21:53.1775107313
$2$ digit numbers that are divisible by 5
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You have $9$ cases where the last digit ends with $5$ and $05$ is not one of them. Hence answer is $9+9=18$.
You can also divide the largest two-digit number $(95)$ by $5$ and subtract the number of one-digit multiples.
$={95\over 5}-{5\over 5} =19-1=18$