new kiddie trick

This trick is for your younger nieces and nephews.  Anyone over 10 or 12 can guess it.  Have them write down a number.  Now have them reverse the digits and sub track the smaller of the two numbers from the larger.  So 209 would be 209 subtracted from 902.  Of course you can not watch what they are writing.  So, you ask them, "do you have the answer yet".  They will say "yes".  you ask them to give you either the first or the last digit.  Their choice.  For the one above they may say the last digit is 3.  Then you say the answer is 693.  Because the answer will always have a 9 in the middle and the other two numbers will add up to 9.  Cool isn't it?