Let me first re-phrase your question: What is the number of (positive) integers less than 10000 (5 digits) and greater than 999 (3 digits)?
The greatest 4 digit integer would be 9999.
The greatest 3 digit integer would be 999.
Let's do some subtraction: 9999 - 999 = 9000
This works because as we count up from 999, each positive integer encountered satisfies your requirements until reaching 10000.
The lowest positive 4-digit number is 1000
-22
There are one thousand. Starting at 2000 and going to 2999
-48
5*5*4*4 = 400
4
22 of them.
The smallest, positive 4-digit multiple of 17 is 1,003.
The lowest positive 4-digit number is 1000
There are 294 such numbers.
from 1000 to 9999, ie 9999 - 999 = 9000
The lowest 4 digit number is -9999. The lowest 4 digit POSITIVE number is 1000.
18 positive integers and 36 integers (negative and positive)
4,000 even numbers, 4,000 odd numbers.
possibly than 20, 3040 3041 etc 3050 3051 etc
1822227777
-22