Question 30
We say an integer $n$ is *naoish* if $n \ge 90$ and the second-to-last digit of $n$ (in decimal notation) is equal to $9$. For example, $10798$, $1999$ and $90$ are naoish, whereas $9900$, $2009$ and $9$ are not. Nino expresses $2020$ as a sum:
$$
2020 = n_{1} + n_{2} + \dots + n_{k}
$$
where each of the $n_j$ is naoish.
What is the smallest positive number $k$ for which Nino can do this?
$$
2020 = n_{1} + n_{2} + \dots + n_{k}
$$
where each of the $n_j$ is naoish.
What is the smallest positive number $k$ for which Nino can do this?