I added together some of my neighbours' house numbers. Can you explain the patterns I noticed?
The puzzle can be solved by finding the values of the unknown digits (all indicated by asterisks) in the squares of the $9\times9$ grid.
Can you find a cuboid that has a surface area of exactly 100 square units. Is there more than one? Can you find them all?
Given the products of diagonally opposite cells - can you complete this Sudoku?
15 = 7 + 8 and 10 = 1 + 2 + 3 + 4. Can you say which numbers can be expressed as the sum of two or more consecutive integers?
A student in a maths class was trying to get some information from her teacher. She was given some clues and then the teacher ended by saying, "Well, how old are they?"
Time for a little mathemagic! Choose any five cards from a pack and show four of them to your partner. How can they work out the fifth?
A monkey with peaches, keeps a fraction of them each day, gives the rest away, and then eats one. How long can his peaches last?
The items in the shopping basket add and multiply to give the same amount. What could their prices be?
Gabriel multiplied together some numbers and then erased them. Can you figure out where each number was?
Move your counters through this snake of cards and see how far you can go. Are you surprised by where you end up?
You need to find the values of the stars before you can apply normal Sudoku rules.
Imagine you have an unlimited number of four types of triangle. How many different tetrahedra can you make?
Investigate the different ways that fifteen schools could have given money in a charity fundraiser.
The clues for this Sudoku are the product of the numbers in adjacent squares.
A Sudoku with clues as ratios.
My two digit number is special because adding the sum of its digits to the product of its digits gives me my original number. What could my number be?
This Sudoku puzzle can be solved with the help of small clue-numbers on the border lines between pairs of neighbouring squares of the grid.
By selecting digits for an addition grid, what targets can you make?
Arrange the four number cards on the grid, according to the rules, to make a diagonal, vertical or horizontal line.
Given the products of adjacent cells, can you complete this Sudoku?
Play the divisibility game to create numbers in which the first two digits make a number divisible by 2, the first three digits make a number divisible by 3...
Charlie and Abi put a counter on 42. They wondered if they could visit all the other numbers on their 1-100 board, moving the counter using just these two operations: x2 and -5. What do you think?
If you take a three by three square on a 1-10 addition square and multiply the diagonally opposite numbers together, what is the difference between these products. Why?
Just four procedures were used to produce a design. How was it done? Can you be systematic and elegant so that someone can follow your logic?
A Sudoku with a twist.
A Sudoku with clues as ratios.
Can you put the 25 coloured tiles into the 5 x 5 square so that no column, no row and no diagonal line have tiles of the same colour in them?
Ben, Jack and Emma passed counters to each other and ended with the same number of counters. How many did they start with?
There is a long tradition of creating mazes throughout history and across the world. This article gives details of mazes you can visit and those that you can tackle on paper.
Do you notice anything about the solutions when you add and/or subtract consecutive negative numbers?
Four numbers on an intersection that need to be placed in the surrounding cells. That is all you need to know to solve this sudoku.
An extra constraint means this Sudoku requires you to think in diagonals as well as horizontal and vertical lines and boxes of nine.
Can you arrange the numbers 1 to 17 in a row so that each adjacent pair adds up to a square number?
This is a variation of sudoku which contains a set of special clue-numbers. Each set of 4 small digits stands for the numbers in the four cells of the grid adjacent to this set.
Make your own double-sided magic square. But can you complete both sides once you've made the pieces?
Each clue in this Sudoku is the product of the two numbers in adjacent cells.
How many different symmetrical shapes can you make by shading triangles or squares?
Place the 16 different combinations of cup/saucer in this 4 by 4 arrangement so that no row or column contains more than one cup or saucer of the same colour.
This article for teachers describes several games, found on the site, all of which have a related structure that can be used to develop the skills of strategic planning.
Here is a Sudoku with a difference! Use information about lowest common multiples to help you solve it.
A 2 by 3 rectangle contains 8 squares and a 3 by 4 rectangle contains 20 squares. What size rectangle(s) contain(s) exactly 100 squares? Can you find them all?
A Sudoku with a twist.
The letters in the following addition sum represent the digits 1 ... 9. If A=3 and D=2, what number is represented by "CAYLEY"?
Find the smallest whole number which, when mutiplied by 7, gives a product consisting entirely of ones.
Solve the equations to identify the clue numbers in this Sudoku problem.
Solve this Sudoku puzzle whose clues are in the form of sums of the numbers which should appear in diagonal opposite cells.
How many solutions can you find to this sum? Each of the different letters stands for a different number.
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?
This Sudoku requires you to do some working backwards before working forwards.