Explaining, convincing and proving

  • Birthday Party
    problem

    Birthday Party

    Age
    11 to 14
    Challenge level
    filled star empty star empty star

    The 30 students in a class have 25 different birthdays between them. What is the largest number that can share any birthday?

  • Old Order
    problem

    Old Order

    Age
    11 to 14
    Challenge level
    filled star empty star empty star

    Who is the youngest in this family?

  • 9 Weights
    problem

    9 Weights

    Age
    11 to 14
    Challenge level
    filled star empty star empty star

    You have been given nine weights, one of which is slightly heavier than the rest. Can you work out which weight is heavier in just two weighings of the balance?

  • Quiz Questions
    problem

    Quiz Questions

    Age
    11 to 14
    Challenge level
    filled star empty star empty star

    Jack does a 20-question quiz. How many questions didn't he attempt?

  • Out of Line
    problem

    Out of Line

    Age
    11 to 14
    Challenge level
    filled star empty star empty star

    Fill in the grid with A-E like a Sudoku. Which letter is in the starred square?

  • Weekly Lies
    problem

    Weekly Lies

    Age
    11 to 14
    Challenge level
    filled star empty star empty star

    Mr Ross tells truths or lies depending on the day of the week. Can you catch him out?

  • Distinct Diagonals
    problem

    Distinct Diagonals

    Age
    11 to 14
    Challenge level
    filled star empty star empty star

    Weekly Problem 21 - 2010
    How many diagonals can you draw on this square...

  • Kept Apart
    problem

    Kept Apart

    Age
    11 to 14
    Challenge level
    filled star empty star empty star

    The squares of this grid contain one of the letters P, Q, R and S. Can you complete this square so that touching squares do not contain the same letter? How many possibilities are there?

  • Would you like a Jelly Baby?
    problem

    Would You Like a Jelly Baby?

    Age
    11 to 14
    Challenge level
    filled star empty star empty star

    What is the smallest number of jelly babies Tom must take, to be certain that he gets at least one of each flavour?

  • Multiplication Magic Square
    problem

    Multiplication Magic Square

    Age
    11 to 14
    Challenge level
    filled star empty star empty star

    Weekly Problem 32 - 2015
    Can you work out the missing numbers in this multiplication magic square?