Multiplication and division

  • A One in Seven Chance
    problem

    A one in seven chance

    Age
    11 to 14
    Challenge level
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    What is the remainder when 2^{164}is divided by 7?
  • A Conversation Piece
    problem

    A conversation piece

    Age
    7 to 11
    Challenge level
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    Take the number 6 469 693 230 and divide it by the first ten prime numbers and you'll find the most beautiful, most magic of all numbers. What is it?
  • 1, 2, 3, 4, 5
    problem

    1, 2, 3, 4, 5

    Age
    7 to 11
    Challenge level
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    Using the numbers 1, 2, 3, 4 and 5 once and only once, and the operations x and ÷ once and only once, what is the smallest whole number you can make?
  • The Number Crunching Machine
    problem

    The number crunching machine

    Age
    7 to 11
    Challenge level
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    Put a number at the top of the machine and collect a number at the bottom. What do you get? Which numbers get back to themselves?
  • Sept03 Sept03 Sept03
    problem

    Sept03 Sept03 Sept03

    Age
    7 to 11
    Challenge level
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    This number has 903 digits. What is the sum of all 903 digits?

  • problem

    Which is quicker?

    Age
    7 to 11
    Challenge level
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    Which is quicker, counting up to 30 in ones or counting up to 300 in tens? Why?

  • Largest product
    problem

    Largest product

    Age
    11 to 14
    Challenge level
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    Which set of numbers that add to 100 have the largest product?
  • Remainders
    problem

    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?

  • Code Breaker
    problem

    Code breaker

    Age
    7 to 11
    Challenge level
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    This problem is based on a code using two different prime numbers less than 10. You'll need to multiply them together and shift the alphabet forwards by the result. Can you decipher the code?
  • The Clockmaker's Birthday Cake
    problem

    The clockmaker's birthday cake

    Age
    7 to 11
    Challenge level
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    The clockmaker's wife cut up his birthday cake to look like a clock face. Can you work out who received each piece?