Explaining, convincing and proving

  • Difference of odd squares
    problem

    Difference of Odd Squares

    Age
    14 to 18
    Challenge level
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    $40$ can be written as $7^2 - 3^2.$ Which other numbers can be written as the difference of squares of odd numbers?

  • The Converse of Pythagoras
    problem

    The Converse of Pythagoras

    Age
    14 to 18
    Challenge level
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    Can you prove that triangles are right-angled when $a^2+b^2=c^2$?

  • Leonardo's Problem
    problem
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    Leonardo's Problem

    Age
    14 to 18
    Challenge level
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    A, B & C own a half, a third and a sixth of a coin collection. Each grab some coins, return some, then share equally what they had put back, finishing with their own share. How rich are they?
  • Shopping basket of various food items.
    problem

    A Long Time at the Till

    Age
    14 to 18
    Challenge level
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    Try to solve this very difficult problem and then study our two suggested solutions. How would you use your knowledge to try to solve variants on the original problem?

  • Transitivity
    article

    Transitivity

    Suppose A always beats B and B always beats C, then would you expect A to beat C? Not always! What seems obvious is not always true. Results always need to be proved in mathematics.

  • Continued Fractions II
    article

    Continued Fractions II

    In this article we show that every whole number can be written as a continued fraction of the form k/(1+k/(1+k/...)).

  • Fractional Calculus III
    article

    Fractional Calculus III

    Fractional calculus is a generalisation of ordinary calculus where you can differentiate n times when n is not a whole number.

  • Euler's Formula and Topology
    article

    Euler's Formula and Topology

    Here is a proof of Euler's formula in the plane and on a sphere together with projects to explore cases of the formula for a polygon with holes, for the torus and other solids with holes and the relationship between Euler's formula and angle deficiency of polyhedra.

  • Euclid's Algorithm II
    article

    Euclid's Algorithm II

    We continue the discussion given in Euclid's Algorithm I, and here we shall discover when an equation of the form ax+by=c has no solutions, and when it has infinitely many solutions.

  • Napoleon's Hat
    problem

    Napoleon's Hat

    Age
    16 to 18
    Challenge level
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    Three equilateral triangles ABC, AYX and XZB are drawn with the point X a moveable point on AB. The points P, Q and R are the centres of the three triangles. What can you say about triangle PQR?