On a sheet of paper write a three-digit number,
where all the digits MUST be different.
Reverse the order of the three-digits
in the number from last to first.
Subtract the smaller number from the larger number.
If the resulting number is a two-digit number, it will be 99.
Place a zero in front of the two-digit number (99) to make it 3 digits.
If the result is already a three-digit number, just continue.
Again reverse the order of the three-digits in this new number from last to first.
Now add both of these new three-digit numbers together.
The result will be always be 1,089. Why?
523 - 325 = 198 + 891 = 1,089
817 - 718 = 099 + 990 = 1,089
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