How many whole numbers have exactly 3 digits hint 999 is the greatest whole number with three digitsint999?

The smallest such number is 100, the largest is 999, so the size of this set is:999 - 100 + 1

Another way to solve this: You have:

* 9 options for the first digit

* 10 options for the second digit

* 10 options for the third digit

Multiply all these numbers together.