Explaining, convincing and proving

  • 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?
  • 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.

  • The London Eye
    problem

    The London Eye

    Age
    14 to 16
    Challenge level
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    The 80 spokes of The London Eye are made from 4 miles of cable. What is the approximate circumference of the wheel?

  • Different Products
    problem

    Different Products

    Age
    14 to 16
    Challenge level
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    Take four consecutive whole numbers. Multiply the first and last numbers together. Multiply the middle pair together. What do you notice?

  • Proximity
    problem

    Proximity

    Age
    14 to 16
    Challenge level
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    We are given a regular icosahedron having three red vertices. Show that it has a vertex that has at least two red neighbours.

  • Gift of Gems
    problem

    Gift of Gems

    Age
    14 to 16
    Challenge level
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    Four jewellers share their stock. Can you work out the relative values of their gems?
  • Long Short
    problem

    Long Short

    Age
    14 to 16
    Challenge level
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    What can you say about the lengths of the sides of a quadrilateral whose vertices are on a unit circle?
  • Janine's Conjecture
    problem

    Janine's Conjecture

    Age
    14 to 16
    Challenge level
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    Janine noticed, while studying some cube numbers, that if you take three consecutive whole numbers and multiply them together and then add the middle number of the three, you get the middle number. Does this always work? Can you prove or disprove this conjecture?