Regular polygons and circles

  • Egyptian Rope
    problem

    Egyptian rope

    Age
    7 to 11
    Challenge level
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    The ancient Egyptians were said to make right-angled triangles using a rope with twelve equal sections divided by knots. What other triangles could you make if you had a rope like this?

  • Squaring the circle
    problem

    Squaring the circle

    Age
    11 to 14
    Challenge level
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    Bluey-green, white and transparent squares with a few odd bits of shapes around the perimeter. But, how many squares are there of each type in the complete circle? Study the picture and make an estimate.
  • Semi-Square
    problem

    Semi-square

    Age
    14 to 16
    Challenge level
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    What is the ratio of the area of a square inscribed in a semicircle to the area of the square inscribed in the entire circle?
  • Crescents and triangles
    problem

    Crescents and triangles

    Age
    14 to 16
    Challenge level
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    Can you find a relationship between the area of the crescents and the area of the triangle?
  • Approximating Pi
    problem

    Approximating pi

    Age
    14 to 18
    Challenge level
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    By inscribing a circle in a square and then a square in a circle find an approximation to pi. By using a hexagon, can you improve on the approximation?
  • Pent
    problem

    Pent

    Age
    14 to 18
    Challenge level
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    The diagram shows a regular pentagon with sides of unit length. Find all the angles in the diagram. Prove that the quadrilateral shown in red is a rhombus.
  • Hex
    problem

    Hex

    Age
    11 to 14
    Challenge level
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    Explain how the thirteen pieces making up the regular hexagon shown in the diagram can be re-assembled to form three smaller regular hexagons congruent to each other.
  • Bull's Eye
    problem

    Bull's eye

    Age
    11 to 14
    Challenge level
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    What fractions of the largest circle are the two shaded regions?
  • Tricircle
    problem

    Tricircle

    Age
    14 to 16
    Challenge level
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    The centre of the larger circle is at the midpoint of one side of an equilateral triangle and the circle touches the other two sides of the triangle. A smaller circle touches the larger circle and two sides of the triangle. If the small circle has radius 1 unit find the radius of the larger circle.