From 1000-9999 how many 4 digit whole numbers are there in all?

Answer 1

Well, let's see now . . .

-- If you were to count from 1 to 9,999 you would count 9,999 numbers.

-- The first 999 of them would have less than 4 digits.

-- So (9,999 - 999) = 9,000 of them would have 4 digits.