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A two digit number can be represented as 10x + y (eg 45 is 10×4 + 5).
If you subtract x and y (45 – 4 -5) you end up with 9x.
If you look at the table all the multiples of 9 are the same and are the item that’s chosen.
It is neat though.
spoil sportViewing 4 posts - 1 through 4 (of 4 total)
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