Similarity and congruence

  • Double Angle Triples
    problem

    Double Angle Triples

    Age
    16 to 18
    Challenge level
    1 out of 3
    Try out this geometry problem involving trigonometry and number theory
  • Golden Triangle
    problem

    Golden Triangle

    Age
    16 to 18
    Challenge level
    2 out of 3
    Three triangles ABC, CBD and ABD (where D is a point on AC) are all isosceles. Find all the angles. Prove that the ratio of AB to BC is equal to the golden ratio.
  • How big?
    problem

    How Big?

    Age
    11 to 14
    Challenge level
    2 out of 3
    If the sides of the triangle in the diagram are 3, 4 and 5, what is the area of the shaded square?
  • All Tied Up
    problem

    All Tied Up

    Age
    14 to 16
    Challenge level
    2 out of 3
    A ribbon runs around a box so that it makes a complete loop with two parallel pieces of ribbon on the top. How long will the ribbon be?
  • Slippage
    problem

    Slippage

    Age
    14 to 16
    Challenge level
    2 out of 3
    A ladder 3m long rests against a wall with one end a short distance from its base. Between the wall and the base of a ladder is a garden storage box 1m tall and 1m high. What is the maximum distance up the wall which the ladder can reach?
  • Sierpinski Triangle
    problem

    Sierpinski Triangle

    Age
    16 to 18
    Challenge level
    2 out of 3
    What is the total area of the triangles remaining in the nth stage of constructing a Sierpinski Triangle? Work out the dimension of this fractal.
  • Squareflake
    problem

    Squareflake

    Age
    16 to 18
    Challenge level
    2 out of 3
    A finite area inside and infinite skin! You can paint the interior of this fractal with a small tin of paint but you could never get enough paint to paint the edge.
  • Strange Rectangle
    problem

    Strange Rectangle

    Age
    16 to 18
    Challenge level
    3 out of 3
    ABCD is a rectangle and P, Q, R and S are moveable points on the edges dividing the edges in certain ratios. Strangely PQRS is always a cyclic quadrilateral and you can find the angles.
  • Flower
    problem

    Flower

    Age
    16 to 18
    Challenge level
    3 out of 3
    Six circles around a central circle make a flower. Watch the flower as you change the radii in this circle packing. Prove that with the given ratios of the radii the petals touch and fit perfectly.
  • Bus Stop
    problem

    Bus Stop

    Age
    14 to 16
    Challenge level
    3 out of 3
    Two buses leave at the same time from two towns Shipton and Veston on the same long road, travelling towards each other. At each mile along the road are milestones. The buses' speeds are constant and in the ratio 5 to 4. The buses travel to and fro between the towns. What milestones are at Shipton and Veston?