Here is a Sudoku with a difference! Use information about lowest common multiples to help you solve it.
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...
Ben, Jack and Emma passed counters to each other and ended with the same number of counters. How many did they start with?
The letters in the following addition sum represent the digits 1 ... 9. If A=3 and D=2, what number is represented by "CAYLEY"?
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?
How many solutions can you find to this sum? Each of the different letters stands for a different number.
Find the values of the nine letters in the sum: FOOT + BALL = GAME
Given the products of adjacent cells, can you complete this Sudoku?
I added together some of my neighbours' house numbers. Can you explain the patterns I noticed?
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?"
Replace the letters with numbers to make the addition work out correctly. R E A D + T H I S = P A G E
The items in the shopping basket add and multiply to give the same amount. What could their prices be?
Given the products of diagonally opposite cells - can you complete this Sudoku?
The clues for this Sudoku are the product of the numbers in adjacent squares.
Find the smallest whole number which, when mutiplied by 7, gives a product consisting entirely of ones.
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?
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.
Each clue in this Sudoku is the product of the two numbers in adjacent cells.
Arrange the four number cards on the grid, according to the rules, to make a diagonal, vertical or horizontal line.
A Latin square of order n is an array of n symbols in which each symbol occurs exactly once in each row and exactly once in each column.
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?
A cinema has 100 seats. Show how it is possible to sell exactly 100 tickets and take exactly £100 if the prices are £10 for adults, 50p for pensioners and 10p for children.
Choose four different digits from 1-9 and put one in each box so that the resulting four two-digit numbers add to a total of 100.
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?
This Sudoku, based on differences. Using the one clue number can you find the solution?
The NRICH team are always looking for new ways to engage teachers and pupils in problem solving. Here we explain the thinking behind maths trails.
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?
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.
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?
This task encourages you to investigate the number of edging pieces and panes in different sized windows.
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.
Can you arrange the numbers 1 to 17 in a row so that each adjacent pair adds up to a square number?
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 Sudoku with clues as ratios.
A particular technique for solving Sudoku puzzles, known as "naked pair", is explained in this easy-to-read article.
A pair of Sudoku puzzles that together lead to a complete solution.
Find out about Magic Squares in this article written for students. Why are they magic?!
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?
It is possible to identify a particular card out of a pack of 15 with the use of some mathematical reasoning. What is this reasoning and can it be applied to other numbers of cards?
Different combinations of the weights available allow you to make different totals. Which totals can you make?
in how many ways can you place the numbers 1, 2, 3 … 9 in the nine regions of the Olympic Emblem (5 overlapping circles) so that the amount in each ring is the same?
A Sudoku with clues as ratios.
You are given the Lowest Common Multiples of sets of digits. Find the digits and then solve the Sudoku.
You have twelve weights, one of which is different from the rest. Using just 3 weighings, can you identify which weight is the odd one out, and whether it is heavier or lighter than the rest?
This Sudoku requires you to do some working backwards before working forwards.
Make your own double-sided magic square. But can you complete both sides once you've made the pieces?
Four small numbers give the clue to the contents of the four surrounding cells.
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?
Add or subtract the two numbers on the spinners and try to complete a row of three. Are there some numbers that are good to aim for?
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.