Explaining, convincing and proving

  • AMGM
    problem

    AMGM

    Age
    14 to 16
    Challenge level
    3 out of 3

    Can you use the diagram to prove the AM-GM inequality?

  • Lens Angle
    problem

    Lens Angle

    Age
    14 to 16
    Challenge level
    3 out of 3

    Find the missing angle between the two secants to the circle when the two angles at the centre subtended by the arcs created by the intersections of the secants and the circle are 50 and 120 degrees.

  • Similarly so
    problem

    Similarly So

    Age
    14 to 16
    Challenge level
    3 out of 3

    ABCD is a square. P is the midpoint of AB and is joined to C. A line from D perpendicular to PC meets the line at the point Q. Prove AQ = AD.

  • Composite Notions
    problem

    Composite Notions

    Age
    14 to 16
    Challenge level
    3 out of 3

    A composite number is one that is neither prime nor 1. Show that 10201 is composite in any base.

  • Triangles within Pentagons
    problem

    Triangles Within Pentagons

    Age
    14 to 16
    Challenge level
    3 out of 3

    Show that all pentagonal numbers are one third of a triangular number.

  • The Great Weights Puzzle
    problem

    The Great Weights Puzzle

    Age
    14 to 16
    Challenge level
    3 out of 3

    You have twelve weights, one of which is different from the rest. Using just 3 weighings, can you identify which weight is the odd one out, and whether it is heavier or lighter than the rest?

  • Small tomato seedlings in pink pots.
    problem

    Square LCM

    Age
    14 to 16
    Challenge level
    3 out of 3

    Using the hcf and lcf of the numerators, can you deduce which of these fractions are square numbers?

  • Close to triangular
    problem

    Close to Triangular

    Age
    14 to 16
    Challenge level
    3 out of 3

    Drawing a triangle is not always as easy as you might think!

  • Geometric Parabola
    problem

    Geometric Parabola

    Age
    14 to 16
    Challenge level
    3 out of 3

    Explore what happens when you draw graphs of quadratic equations with coefficients based on a geometric sequence.

  • Small tomato seedlings in pink pots.
    problem

    Digital Counter

    Age
    14 to 16
    Challenge level
    3 out of 3

    When the numbers from 1 to 1000 are written on a blackboard, which digit appears the most number of times?