How many triple digit numbers are there?

Answer 1

there are 999 - 100 + 1 = 900 positive triple digit positive integers, between 100 and 999.
(e.g. there are 102 - 100 + 1 = 3 triple digit integers between 100 and 102,
namely 100, 101 and 102.)

multiply that by 2 to take in consideration of the negative integers,
you have 1800 triple digit integers.