Column

  1. Math

    Testing for Divisibility

    The crisp new dollar bill that I have just taken from my wallet bears the serial number 24598176. It’s easy to tell that the number is exactly divisible by 2 but not by 5. Is it divisible by 3? by 4? by 11? In a 1962 Scientific American article, Martin Gardner noted that during the […]

    By Ivars Peterson
  2. Math

    Jazzing Up Euclid’s Algorithm

    Earlier this year, the journal Computing in Science & Engineering (CISE) published a list of the top 10 algorithms of the century (see http://computer.org/cise/articles/Top_Algorithms.htm). “Computational algorithms are probably as old as civilization,” Francis Sullivan of the Institute for Defense Analyses’ Center for Computing Sciences in Bowie, Md.