 Write down a three digit number, the digits must be different and the biggest digit must be at the front.
 Reverse the number and write it underneath. (The middle digit should stay in the middle.)
 Subtract the lower from the higher. (If you get "99" put a zero in front to make "099")
 First bit of "magic": your answer will have "9" in the middle. Also the first and last digits will add up to 9.
 Reverse this answer.
 Add the last two answers.
 Second bit of "magic": the total is... 1089

Example a:
741
147
=594
+495
=1089

Example b:
938
839
=099
+990
=1089
