$\sqrt n $ is less than $1$ from $9$

$\sqrt n$ is between $8$ and $10$

$n$ is between $64$ and $100$ (but not $64$ or $100$)

$65,66,67,68,...,99$

$\underbrace{\underbrace{1, 2, 3, ..., 64}_{\text{64 numbers}}, 65, 66, 67, 68, ..., 99}_{\text{99 numbers}}$

$99-64=35$

You can find more short problems, arranged by curriculum topic, in our short problems collection.