Thursday, June 16, 2011
My daughter's school teacher is showing kids some number mysticism.
She told them to take any 3 digit number, e.g.793.
Scramble its digits, e.g. 397.
Subtract from the larger of these two numbers the smaller one: 793-397=396.
Add the digits of the remaining number, e.g. for a number 396 a sum of digits will be 3+9+6=18.
Then, continue adding digits of the last number you got till the sum is just one digit: 1+8=9.
Surprisingly, no matter what number you start from and how you scramble it, the result is always 9!
The puzzle is why is this happening. And the extra credit question is how to explain this to a 8 year old.
Top image by Hryck, distributed under CCL.
Answers accepted all day long on Friday June 17th and Saturday June 18th, on our Family Puzzle Marathon. They will be hidden until Sunday morning (EST) and everyone who solved it will get a puzzle point.