Working systematically

problem
Factor-multiple chains

Age

7 to 11

Challenge level

Can you see how these factor-multiple chains work? Find the chain which contains the smallest possible numbers. How about the largest possible numbers?
problem
What's in the box?

Age

7 to 11

Challenge level

This big box multiplies anything that goes inside it by the same number. If you know the numbers that come out, what multiplication might be going on in the box?
problem
Magnetic personality

Age

7 to 16

Challenge level

60 pieces and a challenge. What can you make and how many of the pieces can you use creating skeleton polyhedra?
problem
Ratio Sudoku 2

Age

11 to 16

Challenge level

A Sudoku with clues as ratios.
problem
Seasonal twin Sudokus

Age

11 to 16

Challenge level

This pair of linked Sudokus matches letters with numbers and hides a seasonal greeting. Can you find it?
problem
One to fifteen

Age

7 to 11

Challenge level

Can you put the numbers from 1 to 15 on the circles so that no consecutive numbers lie anywhere along a continuous straight line?
problem
Noughts and crosses

Age

11 to 14

Challenge level

Ever thought of playing three dimensional Noughts and Crosses? This problem might help you visualise what's involved.
problem
Twin corresponding Sudoku

Age

11 to 18

Challenge level

This sudoku requires you to have "double vision" - two Sudoku's for the price of one
problem
Factors and multiples puzzle

Age

11 to 14

Challenge level

Using your knowledge of the properties of numbers, can you fill all the squares on the board?
problem
Pole star Sudoku

Age

14 to 18

Challenge level

A Sudoku based on clues that give the differences between adjacent cells.