Area - triangles, quadrilaterals, compound shapes

  • Inscribed in a Circle
    problem

    Inscribed in a circle

    Age
    14 to 16
    Challenge level
    filled star filled star empty star
    The area of a square inscribed in a circle with a unit radius is, satisfyingly, 2. What is the area of a regular hexagon inscribed in a circle with a unit radius?
  • Dotty triangles
    problem

    Dotty triangles

    Age
    11 to 14
    Challenge level
    filled star empty star empty star
    Imagine an infinitely large sheet of square dotty paper on which you can draw triangles of any size you wish (providing each vertex is on a dot). What areas is it/is it not possible to draw?
  • Biggest enclosure
    problem

    Biggest enclosure

    Age
    14 to 16
    Challenge level
    filled star filled star empty star
    Three fences of different lengths form three sides of an enclosure. What arrangement maximises the area?
  • Squ-areas
    problem

    Squ-areas

    Age
    14 to 16
    Challenge level
    filled star filled star filled star
    Three squares are drawn on the sides of a triangle ABC. Their areas are respectively 18 000, 20 000 and 26 000 square centimetres. If the outer vertices of the squares are joined, three more triangular areas are enclosed. What is the area of this convex hexagon?
  • Halving the Triangle
    problem

    Halving the triangle

    Age
    16 to 18
    Challenge level
    filled star empty star empty star
    Draw any triangle PQR. Find points A, B and C, one on each side of the triangle, such that the area of triangle ABC is a given fraction of the area of triangle PQR.
  • Triangle Island
    problem

    Triangle island

    Age
    7 to 11
    Challenge level
    filled star filled star filled star
    You have pitched your tent (the red triangle) on an island. Can you move it to the position shown by the purple triangle making sure you obey the rules?
  • Pick's Theorem
    problem

    Pick's theorem

    Age
    14 to 16
    Challenge level
    filled star filled star empty star

    Polygons drawn on square dotty paper have dots on their perimeter (p) and often internal (i) ones as well. Find a relationship between p, i and the area of the polygons.

  • Rati-o
    problem

    Rati-o

    Age
    11 to 14
    Challenge level
    filled star filled star filled star
    Points P, Q, R and S each divide the sides AB, BC, CD and DA respectively in the ratio of 2 : 1. Join the points. What is the area of the parallelogram PQRS in relation to the original rectangle?
  • Disappearing square
    problem

    Disappearing square

    Age
    11 to 14
    Challenge level
    filled star filled star filled star
    Do you know how to find the area of a triangle? You can count the squares. What happens if we turn the triangle on end? Press the button and see. Try counting the number of units in the triangle now. Do you have any interesting findings to report?
  • Overlap
    problem

    Overlap

    Age
    14 to 16
    Challenge level
    filled star filled star empty star

    A red square and a blue square overlap. Is the area of the overlap always the same?