Odd and even numbers

  • Impossible Sandwiches
    article

    Impossible Sandwiches

    In this 7-sandwich: 7 1 3 1 6 4 3 5 7 2 4 6 2 5 there are 7 numbers between the 7s, 6 between the 6s etc. The article shows which values of n can make n-sandwiches and which cannot.
  • All is Number
    article

    All Is Number

    Read all about Pythagoras' mathematical discoveries in this article written for students.

  • Take one example
    article

    Take One Example

    This article introduces the idea of generic proof for younger children and illustrates how one example can offer a proof of a general result through unpacking its underlying structure.
  • Summats Clear
    problem

    Summats Clear

    Age
    16 to 18
    Challenge level
    filled star empty star empty star
    Find the sum, f(n), of the first n terms of the sequence: 0, 1, 1, 2, 2, 3, 3........p, p, p +1, p + 1,..... Prove that f(a + b) - f(a - b) = ab.
  • Arrangements
    problem

    Arrangements

    Age
    7 to 11
    Challenge level
    filled star empty star empty star
    Is it possible to place 2 counters on the 3 by 3 grid so that there is an even number of counters in every row and every column? How about if you have 3 counters or 4 counters or....?
  • Score
    problem

    Score

    Age
    11 to 14
    Challenge level
    filled star filled star empty star
    There are exactly 3 ways to add 4 odd numbers to get 10. Find all the ways of adding 8 odd numbers to get 20. To be sure of getting all the solutions you will need to be systematic. What about a total of 15 with 6 odd numbers?
  • Jenny's Logic
    problem

    Jenny's Logic

    Age
    11 to 14
    Challenge level
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    Weekly Problem 52 - 2009
    How did Jenny figure out that Tom's cards added to an even number?