-の由来:船乗りが樽の入った水が減るたびにつけていた横線の印
+の由来:その横線のついた樽に中身を追加する時縦線を加えて取り消したから
×の由来:十字架を斜めにした。なぜこれをかけるの記号にしたのかは定かではない。
÷の由来:分数を記号化したもの
=の由来:二線間の距離が等しい平行線を意味していることから。
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    +はラテン語の“et”を流して書いたのが由来じゃなかったのか
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