2D shapes and their properties

  • Pentagonal
    problem

    Pentagonal

    Age
    14 to 16
    Challenge level
    filled star empty star empty star
    Can you prove that the sum of the distances of any point inside a square from its sides is always equal (half the perimeter)? Can you prove it to be true for a rectangle or a hexagon?
  • Triangular Hexagons
    problem

    Triangular Hexagons

    Age
    7 to 11
    Challenge level
    filled star empty star empty star
    Investigate these hexagons drawn from different sized equilateral triangles.
  • Like a Circle in a Spiral
    problem

    Like a Circle in a Spiral

    Age
    7 to 16
    Challenge level
    filled star empty star empty star
    A cheap and simple toy with lots of mathematics. Can you interpret the images that are produced? Can you predict the pattern that will be produced using different wheels?
  • Kissing
    problem

    Kissing

    Age
    16 to 18
    Challenge level
    filled star filled star empty star
    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
    filled star filled star empty star
    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
    filled star filled star empty star
    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
    filled star filled star empty star
    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
    filled star filled star empty star
    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
    filled star filled star empty star
    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.