Explaining, convincing and proving

  • Circumference angles
    problem

    Circumference Angles

    Age
    11 to 16
    Challenge level
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    Can you prove the angle properties described by some of the circle theorems?

  • Yih or Luk tsut k'i or Three Men's Morris
    game

    Yih or Luk Tsut K'i or Three Men's Morris

    Age
    11 to 18
    Challenge level
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    Some puzzles requiring no knowledge of knot theory, just a careful inspection of the patterns. A glimpse of the classification of knots and a little about prime knots, crossing numbers and knot arithmetic.

  • The Bridges of Konigsberg
    problem

    The Bridges of Konigsberg

    Age
    11 to 18
    Challenge level
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    Investigate how networks can be used to solve a problem for the 18th Century inhabitants of Konigsberg.

  • What does it all add up to?
    problem

    What Does It All Add Up To?

    Age
    11 to 18
    Challenge level
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    If you take four consecutive numbers and add them together, the answer will always be even. What else do you notice?

  • Doodles
    problem

    Doodles

    Age
    14 to 16
    Challenge level
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    Draw a 'doodle' - a closed intersecting curve drawn without taking pencil from paper. What can you prove about the intersections?

  • Russian Cubes
    problem

    Russian Cubes

    Age
    14 to 16
    Challenge level
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    I want some cubes painted with three blue faces and three red faces. How many different cubes can be painted like that?

  • Natural Sum
    problem

    Natural Sum

    Age
    14 to 16
    Challenge level
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    The picture illustrates the sum 1 + 2 + 3 + 4 = (4 × 5)/2. Prove the general formula for the sum of the first n natural numbers and the formula for the sum of the cubes of the first n natural numbers.

  • N000ughty thoughts
    problem

    N000ughty

    Age
    14 to 16
    Challenge level
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    How many noughts are at the end of these giant numbers?