Explaining, convincing and proving

  • Mediant madness
    problem

    Mediant Madness

    Age
    14 to 16
    Challenge level
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    Kyle and his teacher disagree about his test score - who is right?

  • Archimedes and numerical roots
    problem

    Archimedes and Numerical Roots

    Age
    14 to 16
    Challenge level
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    The problem is how did Archimedes calculate the lengths of the sides of the polygons which needed him to be able to calculate square roots?

  • Parallel Universe
    problem

    Parallel Universe

    Age
    14 to 16
    Challenge level
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    An equilateral triangle is constructed on BC. A line QD is drawn, where Q is the midpoint of AC. Prove that AB // QD.

  • Cross-Country Race
    problem

    Cross-Country Race

    Age
    14 to 16
    Challenge level
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    Eight children enter the autumn cross-country race at school. How many possible ways could they come in at first, second and third places?

  • Ordered Sums
    problem

    Ordered Sums

    Age
    14 to 16
    Challenge level
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    Let a(n) be the number of ways of expressing the integer n as an ordered sum of 1's and 2's. Let b(n) be the number of ways of expressing n as an ordered sum of integers greater than 1. (i) Calculate a(n) and b(n) for n<8. What do you notice about these sequences? (ii) Find a relation between a(p) and b(q). (iii) Prove your conjectures.

  • Circle Box
    problem

    Circle Box

    Age
    14 to 16
    Challenge level
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    It is obvious that we can fit four circles of diameter 1 unit in a square of side 2 without overlapping. What is the smallest square into which we can fit 3 circles of diameter 1 unit?

  • Triangles within Squares
    problem

    Triangles Within Squares

    Age
    14 to 16
    Challenge level
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    Can you find a rule which relates triangular numbers to square numbers?

  • Day of the Triffids
    problem

    Day of the Triffids

    Age
    14 to 16
    Challenge level
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    Jasmine buys three different types of plant. How many triffids did she buy?

  • Folding Fractions
    problem

    Folding Fractions

    Age
    14 to 16
    Challenge level
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    What fractions can you divide the diagonal of a square into by simple folding?

  • L-triominoes
    problem

    L-Triominoes

    Age
    14 to 16
    Challenge level
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    L triominoes can fit together to make larger versions of themselves. Is every size possible to make in this way?