I came across this "trick" (if you will) and I was wondering if the community could give me some input as to how to show the algebra behind this "trick". The "trick" states: "1. Think of a 3-digit number. 2. Add the digits. 3. Subtract the number you got from step 2 from your original 3-digit number. You should now have a 2 or 3-digit number. Cross off one of the digits. Tell me the number you have left and I can guess the digit you crossed off." Any ideas?

Note by Chillwillybillysilly .
9 months, 2 weeks ago

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