Question

How many whole numbers have exactly 3 digits

Answer 1

999 because If you add one to 999 it's 1,000 and you'll go into the 4 digits

Answer 2

The biggest one is 999.

If you started counting from 1 to 999, you would count to 99
before you get to the first 3-digit number.

So there are (999 - 99) = 900 of them.