Posted on Saturday, 29 January 2011

例えば上記クレジットカード番号（他のどんなクレジットカード番号でもOKです）を例にとってみましょう…


元の数）4417 1234 5678 9113


この右の2桁目からひとつ置きに2倍に掛けてみると…


8 2 2 6 10 14 18 2


それを、元の数の右1桁目からひとつ置きに拾った数…


4 7 2 4 6 8 1 3


に足します。2桁の数は十の位と1の位を足して1桁にしましょう。


式）8＋4＋2＋7＋2＋2＋6＋4＋1＋0＋6＋1＋4＋8＋1＋8＋1＋2＋3＝70


この最後に出た和が10で割れる数なら、そのクレジットカードは有効です。
10で余りが出たら無効あるいは偽造ですよ。さ、自分のカードで試してみてね！

知ってる？ クレジットカード番号の意味と暗算認証術 : ギズモード・ジャパン

ほほ～

(via naok)

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