The 1089 Phenomenon

Take any three-digit number in which the first and last digits are different.  Reverse the digits to get a new number, so now you have two numbers, and each one is the reverse of the other.  Subtract the smaller from the larger to get a third three-digit number.  (If subtracting gives you a two digit number, then please treat it as a three-digit number whose first digit is zero.)  Now add this number to its reverse.  The result will be 1089.

Why?

Example:

571-175 = 396,
396+693 = 1089

Click here for the answer.

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The webmaster and author of the Math Help site is Graeme McRae.
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