Divisibility

  • Dirisibly Yours
    problem

    Dirisibly Yours

    Age
    16 to 18
    Challenge level

    Find and explain a short and neat proof that 5^(2n+1) + 11^(2n+1) + 17^(2n+1) is divisible by 33 for every non negative integer n.

  • Digital Roots
    article

    Digital Roots

    In this article for teachers, Bernard Bagnall describes how to find digital roots and suggests that they can be worth exploring when confronted by a sequence of numbers.

  • Divisibility Tests
    article

    Divisibility Tests

    This article explains various divisibility rules and why they work. An article to read with pencil and paper handy.

  • The Chinese Remainder Theorem
    article

    The Chinese Remainder Theorem

    In this article we shall consider how to solve problems such as "Find all integers that leave a remainder of 1 when divided by 2, 3, and 5."

  • The Knapsack Problem and Public Key Cryptography
    article

    The Knapsack Problem and Public Key Cryptography

    An example of a simple Public Key code, called the Knapsack Code is described in this article, alongside some information on its origins. A knowledge of modular arithmetic is useful.

  • Public Key Cryptography
    article

    Public Key Cryptography

    An introduction to coding and decoding messages and the maths behind how to secretly share information.
Displaying 71 - 76 of 76