A probability problem by Naren Bhandari

Relevant wiki: Rule of Product - Intermediate

Here we can see that there are three possible places for the numbers _ _ __ .

In first place we can put all numbers from 1 to 9 . [ So $\boxed{9}$ Numbers]

In second place there are Again $\boxed{9}$ possible numbers , exculding the one we used last time and Including 0 this time.

So Now we have $\boxed{8}$ numbers for the next place .

Hence The total numbers = $\boxed{9 * 9 * 8} = \boxed{648}$