Explaining, convincing and proving

  • Always Perfect
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    Always Perfect

    Age
    14 to 18
    Challenge level
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    Show that if you add 1 to the product of four consecutive numbers the answer is ALWAYS a perfect square.

  • Leonardo's 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?

  • Polynomial Relations
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    Polynomial Relations

    Age
    16 to 18
    Challenge level
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    Given any two polynomials in a single variable it is always possible to eliminate the variable and obtain a formula showing the relationship between the two polynomials. Try this one.

  • How Many Solutions?
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    How Many Solutions?

    Age
    16 to 18
    Challenge level
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    Find all the solutions to the this equation.

  • Prime AP
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    Prime AP

    Age
    16 to 18
    Challenge level
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    What can you say about the common difference of an AP where every term is prime?

  • Flexi Quads
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    Flexi Quads

    Age
    16 to 18
    Challenge level
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    A quadrilateral changes shape with the edge lengths constant. Show the scalar product of the diagonals is constant. If the diagonals are perpendicular in one position are they always perpendicular?

  • Quadratic Harmony
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    Quadratic Harmony

    Age
    16 to 18
    Challenge level
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    Find all positive integers a and b for which the two equations: x^2-ax+b = 0 and x^2-bx+a = 0 both have positive integer solutions.

  • Parabella
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    Parabella

    Age
    16 to 18
    Challenge level
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    This is a beautiful result involving a parabola and parallels.

  • Sixty-Seven Squared
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    Sixty-Seven Squared

    Age
    16 to 18
    Challenge level
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    Evaluate these powers of 67. What do you notice? Can you convince someone what the answer would be to (a million sixes followed by a 7) squared?

  • Three by One
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    Three by One

    Age
    16 to 18
    Challenge level
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    There are many different methods to solve this geometrical problem - how many can you find?