Explaining, convincing and proving

  • Composite Notions
    problem

    Composite Notions

    Age
    14 to 16
    Challenge level
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    A composite number is one that is neither prime nor 1. Show that 10201 is composite in any base.

  • Triangles within Pentagons
    problem

    Triangles Within Pentagons

    Age
    14 to 16
    Challenge level
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    Show that all pentagonal numbers are one third of a triangular number.

  • The Great Weights Puzzle
    problem

    The Great Weights Puzzle

    Age
    14 to 16
    Challenge level
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    You have twelve weights, one of which is different from the rest. Using just 3 weighings, can you identify which weight is the odd one out, and whether it is heavier or lighter than the rest?

  • Square LCM
    problem

    Square LCM

    Age
    14 to 16
    Challenge level
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    Using the hcf and lcf of the numerators, can you deduce which of these fractions are square numbers?

  • Close to triangular
    problem

    Close to Triangular

    Age
    14 to 16
    Challenge level
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    Drawing a triangle is not always as easy as you might think!

  • Geometric Parabola
    problem

    Geometric Parabola

    Age
    14 to 16
    Challenge level
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    Explore what happens when you draw graphs of quadratic equations with coefficients based on a geometric sequence.

  • Digital Counter
    problem

    Digital Counter

    Age
    14 to 16
    Challenge level
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    When the numbers from 1 to 1000 are written on a blackboard, which digit appears the most number of times?

  • Dalmatians
    problem

    Dalmatians

    Age
    14 to 18
    Challenge level
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    Investigate the sequences obtained by starting with any positive 2 digit number (10a+b) and repeatedly using the rule 10a+b maps to 10b-a to get the next number in the sequence.

  • Road maker
    problem

    Road Maker

    Age
    14 to 18
    Challenge level
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    Which of these roads will satisfy a Munchkin builder?

  • IFFY triangles
    problem

    IFFY Triangles

    Age
    14 to 18
    Challenge level
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    Can you prove these triangle theorems both ways?