Pythagoras' theorem

  • Two circles
    problem

    Two Circles

    Age
    14 to 16
    Challenge level
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    Draw two circles, each of radius 1 unit, so that each circle goes through the centre of the other one. What is the area of the overlap?
  • Square Pegs
    problem

    Square Pegs

    Age
    11 to 14
    Challenge level
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    Which is a better fit, a square peg in a round hole or a round peg in a square hole?
  • Isosceles
    problem

    Isosceles

    Age
    11 to 14
    Challenge level
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    Prove that a triangle with sides of length 5, 5 and 6 has the same area as a triangle with sides of length 5, 5 and 8. Find other pairs of non-congruent isosceles triangles which have equal areas.
  • Trice
    problem

    Trice

    Age
    11 to 14
    Challenge level
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    ABCDEFGH is a 3 by 3 by 3 cube. Point P is 1/3 along AB (that is AP : PB = 1 : 2), point Q is 1/3 along GH and point R is 1/3 along ED. What is the area of the triangle PQR?
  • A chordingly
    problem

    A Chordingly

    Age
    11 to 14
    Challenge level
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    Find the area of the annulus in terms of the length of the chord which is tangent to the inner circle.
  • Pareq Calc
    problem

    Pareq Calc

    Age
    14 to 16
    Challenge level
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    Triangle ABC is an equilateral triangle with three parallel lines going through the vertices. Calculate the length of the sides of the triangle if the perpendicular distances between the parallel lines are 1 unit and 2 units.
  • Semi-Square
    problem

    Semi-Square

    Age
    14 to 16
    Challenge level
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    What is the ratio of the area of a square inscribed in a semicircle to the area of the square inscribed in the entire circle?
  • Take a square
    problem

    Take a Square

    Age
    14 to 16
    Challenge level
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    Cut off three right angled isosceles triangles to produce a pentagon. With two lines, cut the pentagon into three parts which can be rearranged into another square.
  • Cutting a Cube
    problem

    Cutting a Cube

    Age
    11 to 14
    Challenge level
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    A half-cube is cut into two pieces by a plane through the long diagonal and at right angles to it. Can you draw a net of these pieces? Are they identical?
  • In a Spin
    problem

    In a Spin

    Age
    14 to 16
    Challenge level
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    What is the volume of the solid formed by rotating this right angled triangle about the hypotenuse?