Multiplication and division

  • 3388
    problem

    3388

    Age
    11 to 14
    Challenge level
    2 out of 3

    Using some or all of the operations of addition, subtraction, multiplication and division and using the digits 3, 3, 8 and 8 each once and only once make an expression equal to 24.

  • Small tomato seedlings in pink pots.
    problem

    Adjacent Factors

    Age
    11 to 14
    Challenge level
    2 out of 3

    Two numbers can be placed adjacent if one of them divides the other. Using only $1,...,10$, can you write the longest such list?

  • Small tomato seedlings in pink pots.
    problem

    Rolling Along the Trail

    Age
    11 to 14
    Challenge level
    2 out of 3

    What could be the scores from five throws of this dice?

  • Factoring factorials
    problem

    Factoring Factorials

    Age
    11 to 14
    Challenge level
    3 out of 3

    Find the highest power of 11 that will divide into 1000! exactly.

  • One O Five
    problem

    One O Five

    Age
    11 to 14
    Challenge level
    3 out of 3

    You can work out the number someone else is thinking of as follows. Ask a friend to think of any natural number less than 100. Then ask them to tell you the remainders when this number is divided by 3, 5 and by 7...

  • Powerful factorial
    problem

    Powerful Factorial

    Age
    11 to 14
    Challenge level
    3 out of 3

    6! = 6 × 5 × 4 × 3 × 2 × 1. The highest power of 2 that divides exactly into 6! is 4 since (6!) / (2^4) = 45. What is the highest power of two that divides exactly into 100!?

  • Please Explain
    problem

    Please Explain

    Age
    11 to 14
    Challenge level
    3 out of 3

    Visitors to Earth from the distant planet of Zub-Zorna were amazed when they found out that when the digits in this multiplication were reversed, the answer was the same! Find a way to explain why this works.

  • Plastic human skeleton on a blue background.
    problem

    Skeleton

    Age
    11 to 14
    Challenge level
    3 out of 3

    Can you reconstruct the long division calculation from the 'skeleton'?

  • Alphabetti Sudoku
    problem

    Alphabetti Sudoku

    Age
    11 to 16
    Challenge level
    1 out of 3

    This Sudoku requires you to do some working backwards before working forwards.

  • What is the question?
    problem

    What Is the Question?

    Age
    11 to 16
    Challenge level
    1 out of 3
    These pictures and answers leave the viewer with the problem "What is the Question". Can you give the question and how the answer follows?