Explaining, convincing and proving

  • The square under the hypotenuse
    problem
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    The Square Under the Hypotenuse

    Age
    14 to 16
    Challenge level
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    Can you work out the side length of a square that just touches the hypotenuse of a right angled triangle?

  • Cosines Rule
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    Cosines Rule

    Age
    14 to 16
    Challenge level
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    Three points A, B and C lie in this order on a line, and P is any point in the plane. Use the Cosine Rule to prove the following statement.

  • Latin Numbers
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    Latin Numbers

    Age
    14 to 16
    Challenge level
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    Can you create a Latin Square from multiples of a six digit number?

  • Two blank square picture frames on a wooden floor.
    problem
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    2-Digit Square

    Age
    14 to 16
    Challenge level
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    A 2-digit number is squared. When this 2-digit number is reversed and squared, the difference between the squares is also a square. What is the 2-digit number?

  • Compare Areas
    problem
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    Compare Areas

    Age
    14 to 16
    Challenge level
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    Which has the greatest area, a circle or a square, inscribed in an isosceles right angle triangle?

  • Napkin
    problem
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    Napkin

    Age
    14 to 16
    Challenge level
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    A napkin is folded so that a corner coincides with the midpoint of an opposite edge. Investigate the three triangles formed.

  • Angle Trisection
    problem
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    Angle Trisection

    Age
    14 to 16
    Challenge level
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    It is impossible to trisect an angle using only ruler and compasses but it can be done using a carpenter's square.

  • Lens Angle
    problem
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    Lens Angle

    Age
    14 to 16
    Challenge level
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    Find the missing angle between the two secants to the circle when the two angles at the centre subtended by the arcs created by the intersections of the secants and the circle are 50 and 120 degrees.
  • Hexy-Metry
    problem
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    Hexy-Metry

    Age
    14 to 16
    Challenge level
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    A hexagon, with sides alternately a and b units in length, is inscribed in a circle. How big is the radius of the circle?

  • Squirty
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    Squirty

    Age
    14 to 16
    Challenge level
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    Using a ruler, pencil and compasses only, it is possible to construct a square inside any triangle so that all four vertices touch the sides of the triangle.