Similarity and congruence

  • Two Ladders
    problem
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    Two ladders

    Age
    14 to 16
    Challenge level
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    Two ladders are propped up against facing walls. At what height do the ladders cross?

  • Sitting Pretty
    problem
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    Sitting pretty

    Age
    14 to 16
    Challenge level
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    A circle of radius r touches two sides of a right angled triangle, sides x and y, and has its centre on the hypotenuse. Can you prove the formula linking x, y and r?

  • Folding Squares
    problem

    Folding squares

    Age
    14 to 16
    Challenge level
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    The diagonal of a square intersects the line joining one of the unused corners to the midpoint of the opposite side. What do you notice about the line segments produced?
  • Overlap
    problem

    Overlap

    Age
    14 to 16
    Challenge level
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    A red square and a blue square overlap. Is the area of the overlap always the same?

  • Triangle in a Triangle
    problem
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    Triangle in a triangle

    Age
    14 to 16
    Challenge level
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    Can you work out the fraction of the original triangle that is covered by the inner triangle?

  • Trapezium Four
    problem
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    Trapezium four

    Age
    14 to 16
    Challenge level
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    The diagonals of a trapezium divide it into four parts. Can you create a trapezium where three of those parts are equal in area?

  • Nicely Similar
    problem
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    Nicely similar

    Age
    14 to 16
    Challenge level
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    If the hypotenuse (base) length is 100cm and if an extra line splits the base into 36cm and 64cm parts, what were the side lengths for the original right-angled triangle?

  • Folding Fractions
    problem

    Folding fractions

    Age
    14 to 16
    Challenge level
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    What fractions can you divide the diagonal of a square into by simple folding?
  • The square under the hypotenuse
    problem
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    The square under the hypotenuse

    Age
    14 to 16
    Challenge level
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    Can you work out the side length of a square that just touches the hypotenuse of a right angled triangle?