Always End With 1089

=== Add two numbers together and always end with 1089. Here is How: === Pick a three digit number.The three numbers used must be different*. i.e. 123

Reverse that number. 123 becomes 321

Take the smallest three digit number from the largest. 321 − 123 = 198

Take the answer and reverse that number. 198 becomes 891

Add that number to the answer of the subtraction. 891 + 198 = 1089

The answer will be 1089!
==== So why does it do this? Find out here ====

A Little Footnote
But I ended with 198 not 1089 ... !

This happens if you pick a number like 546.

546 goes like this: 645−546=99, then 99+99=198.

BUT if you assume that 099 is a 3 digit number, you will get: 990−099=891, and 891+198=1089

* If you don't pick three different numbers then this might happen: 343−343=0, 0+0=0