2D shapes and their properties

  • Kissing
    problem

    Kissing

    Age
    16 to 18
    Challenge level
    2 out of 3
    Two perpendicular lines are tangential to two identical circles that touch. What is the largest circle that can be placed in between the two lines and the two circles and how would you construct it?
  • Floored
    problem

    Floored

    Age
    14 to 16
    Challenge level
    2 out of 3
    A floor is covered by a tessellation of equilateral triangles, each having three equal arcs inside it. What proportion of the area of the tessellation is shaded?
  • Three four five
    problem

    Three Four Five

    Age
    14 to 16
    Challenge level
    2 out of 3
    Two semi-circles (each of radius 1/2) touch each other, and a semi-circle of radius 1 touches both of them. Find the radius of the circle which touches all three semi-circles.
  • Holly
    problem

    Holly

    Age
    14 to 16
    Challenge level
    2 out of 3
    The ten arcs forming the edges of the "holly leaf" are all arcs of circles of radius 1 cm. Find the length of the perimeter of the holly leaf and the area of its surface.
  • The medieval octagon
    problem

    The Medieval Octagon

    Age
    14 to 16
    Challenge level
    2 out of 3
    Medieval stonemasons used a method to construct octagons using ruler and compasses... Is the octagon regular? Proof please.
  • Tricircle
    problem

    Tricircle

    Age
    14 to 16
    Challenge level
    2 out of 3
    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.
  • Squaring the circle
    problem

    Squaring the Circle

    Age
    11 to 14
    Challenge level
    2 out of 3
    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.
  • Playground Snapshot
    problem

    Playground Snapshot

    Age
    7 to 14
    Challenge level
    2 out of 3
    The image in this problem is part of a piece of equipment found in the playground of a school. How would you describe it to someone over the phone?
  • Lunar Angles
    problem

    Lunar Angles

    Age
    16 to 18
    Challenge level
    2 out of 3
    What is the sum of the angles of a triangle whose sides are circular arcs on a flat surface? What if the triangle is on the surface of a sphere?
  • Spirostars
    problem

    Spirostars

    Age
    16 to 18
    Challenge level
    2 out of 3
    A spiropath is a sequence of connected line segments end to end taking different directions. The same spiropath is iterated. When does it cycle and when does it go on indefinitely?