Explaining, convincing and proving

problem

Thirty Nine, Seventy Five

Age

11 to 14

Challenge level

1 out of 3

We have exactly 100 coins. There are five different values of coins. We have decided to buy a piece of computer software for 39.75. We have the correct money, not a penny more, not a penny less! Can you discover what the five different types of coins are worth and how many of each we have saved?
problem

Concrete Wheel

Age

11 to 14

Challenge level

1 out of 3

A huge wheel is rolling past your window. What do you see?
problem

Birthday Party

Age

11 to 14

Challenge level

1 out of 3

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

Old Order

Age

11 to 14

Challenge level

1 out of 3

Who is the youngest in this family?
problem

9 Weights

Age

11 to 14

Challenge level

1 out of 3

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?
problem

Quiz Questions

Age

11 to 14

Challenge level

1 out of 3

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

Out of Line

Age

11 to 14

Challenge level

1 out of 3

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

Multiples Sudoku

Age

11 to 14

Challenge level

1 out of 3

Each clue in this Sudoku is the product of the two numbers in adjacent cells.
problem

Weekly Lies

Age

11 to 14

Challenge level

1 out of 3

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

Distinct Diagonals

Age

11 to 14

Challenge level

1 out of 3

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