Divisibility

  • A chopped carrot beside a whole carrot. The carrot top sits away from the chopped carrot.
    problem
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    Remainders

    Age
    7 to 14
    Challenge level
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    I'm thinking of a number. My number is both a multiple of 5 and a multiple of 6. What could my number be?

  • An American flag waving in the wind.
    problem
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    American Billions

    Age
    11 to 14
    Challenge level
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    Play the divisibility game to create numbers in which the first two digits make a number divisible by 2, the first three digits make a number divisible by 3...

  • Elevenses
    problem
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    Elevenses

    Age
    11 to 14
    Challenge level
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    How many pairs of numbers can you find that add up to a multiple of 11? Do you notice anything interesting about your results?

  • Going round in circles
    problem
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    Going Round in Circles

    Age
    11 to 14
    Challenge level
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    Mathematicians are always looking for efficient methods for solving problems. How efficient can you be?

  • What numbers can we make?
    problem
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    What Numbers Can We Make?

    Age
    11 to 14
    Challenge level
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    Imagine we have four bags containing a large number of 1s, 4s, 7s and 10s. What numbers can we make?

  • Counting Factors
    problem
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    Counting Factors

    Age
    11 to 14
    Challenge level
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    Is there an efficient way to work out how many factors a large number has?

  • Legs Eleven
    problem
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    Legs Eleven

    Age
    11 to 14
    Challenge level
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    Take any four digit number. Move the first digit to the end and move the rest along. Now add your two numbers. Did you get a multiple of 11?

  • Peaches today, Peaches tomorrow...
    problem
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    Peaches Today, Peaches Tomorrow...

    Age
    11 to 14
    Challenge level
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    A monkey with peaches, keeps a fraction of them each day, gives the rest away, and then eats one. How long can his peaches last?

  • Power mad!
    problem
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    Power Mad!

    Age
    11 to 14
    Challenge level
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    Powers of numbers behave in surprising ways. Take a look at some of these and try to explain why they are true.

  • What numbers can we make now?
    problem
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    What Numbers Can We Make Now?

    Age
    11 to 14
    Challenge level
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    Imagine we have four bags containing numbers from a sequence. What numbers can we make now?