Reflections

  • Semaphore
    problem

    Semaphore

    Age
    11 to 14
    Challenge level
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    I am standing behind five pupils who are signalling a five-digit number to someone on the opposite side of the playground. What number is actually being signalled?

  • Reading from Behind
    problem

    Reading From Behind

    Age
    11 to 14
    Challenge level
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    Can you find the time between 3 o'clock and 10 o'clock when my digital clock looks the same from both the front and back?

  • Simplifying Transformations
    problem

    Simplifying Transformations

    Age
    11 to 14
    Challenge level
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    How many different transformations can you find made up from combinations of R, S and their inverses? Can you be sure that you have found them all?

  • A Roll Of Patterned Paper
    problem

    A Roll of Patterned Paper

    Age
    14 to 16
    Challenge level
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    A design is repeated endlessly along a line - rather like a stream of paper coming off a roll. Make a strip that matches itself after rotation, or after reflection

  • One Reflection Implies Another
    problem

    One Reflection Implies Another

    Age
    14 to 16
    Challenge level
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    When a strip has vertical symmetry there always seems to be a second place where a mirror line could go. Perhaps you can find a design that has only one mirror line across it. Or, if you thought that was impossible, could you explain why ?

  • The Fire-fighter's Car Keys
    problem

    The Fire-Fighter's Car Keys

    Age
    14 to 16
    Challenge level
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    A fire-fighter needs to fill a bucket of water from the river and take it to a fire. What is the best point on the river bank for the fire-fighter to fill the bucket?

  • A Problem of time
    problem

    A Problem of Time

    Age
    14 to 16
    Challenge level
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    Consider a watch face which has identical hands and identical marks for the hours. It is opposite to a mirror. When is the time as read direct and in the mirror exactly the same between 6 and 7?
  • Orbiting Billiard Balls
    problem

    Orbiting Billiard Balls

    Age
    14 to 16
    Challenge level
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    What angle is needed for a ball to do a circuit of the billiard table and then pass through its original position?

  • Rotations Are Not Single Round Here
    problem

    Rotations Are Not Single Round Here

    Age
    14 to 16
    Challenge level
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    I noticed this about streamers that have rotation symmetry : if there was one centre of rotation there always seems to be a second centre that also worked. Can you find a design that has only one centre of rotation ? Or if you thought that was impossible, could you say why ?

  • Flipping Twisty Matrices
    problem

    Flipping Twisty Matrices

    Age
    14 to 18
    Challenge level
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    Investigate the transformations of the plane given by the 2 by 2 matrices with entries taking all combinations of values 0, -1 and +1.