Uncommon Knowledge

Uncommon Knowledge: Was + or = invented first?

February 17, 2015

Math Formulas Tie | UncommonGoods

It seems hard to believe that +, = and all the other symbols of the mathematical world haven’t always simply existed like they do now. But in fact, the plus sign didn’t come around until the 15th century. A symbolic contraction of the Latin word et, meaning “and,” it took another hundred years or so for it to be widely adopted. Maybe it was that handy “and” sign that inspired Robert Recorde, in 1557, to use two parallel lines to represent “is equal to.” But if we know when these math symbols were invented, it brings up the question of what mathematicians were using before that. The horrifying answer? Story problems. Here is an actual question from a 9th century, Persian text about algebra: “I have divided ten into two parts, and multiplying one of these by the other, the result was twenty-one.” Shiver.

Math Formulas Tie, $45


  • Reply Lisa February 17, 2015 at 10:58 pm

    I enjoyed reading Interesting facts about the symbols of mathematics and Nathan’s adventurous life! Is there a DNA tie with Ribosomes and exosomes?

  • Reply Susan Parry March 2, 2015 at 6:21 pm

    Just wanted to say you’re brilliant. I love “trivia” articles. I actually think the word “trivia” does itself an injustice as all knowledge is very important!

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