Prime numbers

  • A Biggy
    problem

    A Biggy

    Age
    14 to 16
    Challenge level
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    Find the smallest positive integer N such that N/2 is a perfect cube, N/3 is a perfect fifth power and N/5 is a perfect seventh power.

  • Different by One
    problem

    Different by One

    Age
    14 to 16
    Challenge level
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    Can you make lines of Cuisenaire rods that differ by 1?
  • Never Prime
    problem

    Never Prime

    Age
    14 to 16
    Challenge level
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    If a two digit number has its digits reversed and the smaller of the two numbers is subtracted from the larger, prove the difference can never be prime.

  • Factoring a million
    problem

    Factoring a Million

    Age
    14 to 16
    Challenge level
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    In how many ways can the number 1 000 000 be expressed as the product of three positive integers?

  • There's always One isn't there
    problem

    There's Always One Isn't There

    Age
    14 to 16
    Challenge level
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    Take any pair of numbers, say 9 and 14. Take the larger number, fourteen, and count up in 14s. Then divide each of those values by the 9, and look at the remainders.

  • Three Primes
    problem

    Three Primes

    Age
    14 to 16
    Challenge level
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    Weekly Problem 6 - 2010
    Can you find three primes such that their product is exactly five times their sum? Do you think you have found all possibilities?

  • Prime sequences
    problem

    Prime Sequences

    Age
    16 to 18
    Challenge level
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    This group tasks allows you to search for arithmetic progressions in the prime numbers. How many of the challenges will you discover for yourself?

  • Can it be?
    problem

    Can It Be?

    Age
    16 to 18
    Challenge level
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    When if ever do you get the right answer if you add two fractions by adding the numerators and adding the denominators?

  • Factorial Fun
    problem

    Factorial Fun

    Age
    16 to 18
    Challenge level
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    How many divisors does factorial n (n!) have?

  • Rarity
    problem

    Rarity

    Age
    16 to 18
    Challenge level
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    Show that it is rare for a ratio of ratios to be rational.