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You are given the Lowest Common Multiples of sets of digits. Find the digits and then solve the Sudoku.

In this article, the NRICH team describe the process of selecting solutions for publication on the site.

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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.

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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?

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You need to find the values of the stars before you can apply normal Sudoku rules.

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The challenge is to find the values of the variables if you are to solve this Sudoku.

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.

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An extra constraint means this Sudoku requires you to think in diagonals as well as horizontal and vertical lines and boxes of nine.

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Solve the equations to identify the clue numbers in this Sudoku problem.

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In this Sudoku, there are three coloured "islands" in the 9x9 grid. Within each "island" EVERY group of nine cells that form a 3x3 square must contain the numbers 1 through 9.

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

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.

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Replace the letters with numbers to make the addition work out correctly. R E A D + T H I S = P A G E

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.

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I added together some of my neighbours' house numbers. Can you explain the patterns I noticed?

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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.

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Do you notice anything about the solutions when you add and/or subtract consecutive negative numbers?

This second Sudoku article discusses "Corresponding Sudokus" which are pairs of Sudokus with terms that can be matched using a substitution rule.

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Four small numbers give the clue to the contents of the four surrounding cells.

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A pair of Sudoku puzzles that together lead to a complete solution.

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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?

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Label the joints and legs of these graph theory caterpillars so that the vertex sums are all equal.

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Find all the ways of placing the numbers 1 to 9 on a W shape, with 3 numbers on each leg, so that each set of 3 numbers has the same total.

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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?

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Special clue numbers related to the difference between numbers in two adjacent cells and values of the stars in the "constellation" make this a doubly interesting problem.

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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.

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A man has 5 coins in his pocket. Given the clues, can you work out what the coins are?

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Advent Calendar 2011 - a mathematical activity for each day during the run-up to Christmas.

A particular technique for solving Sudoku puzzles, known as "naked pair", is explained in this easy-to-read article.

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How have "Warmsnug" arrived at the prices shown on their windows? Which window has been given an incorrect price?

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Gabriel multiplied together some numbers and then erased them. Can you figure out where each number was?

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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?

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This sudoku requires you to have "double vision" - two Sudoku's for the price of one

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A pair of Sudokus with lots in common. In fact they are the same problem but rearranged. Can you find how they relate to solve them both?

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Investigate the different ways that fifteen schools could have given money in a charity fundraiser.

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This task encourages you to investigate the number of edging pieces and panes in different sized windows.

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Take three whole numbers. The differences between them give you three new numbers. Find the differences between the new numbers and keep repeating this. What happens?

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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?

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Can you arrange the numbers 1 to 17 in a row so that each adjacent pair adds up to a square number?

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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?

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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?

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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?"

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

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Mr Smith and Mr Jones are two maths teachers. By asking questions, the answers to which may be right or wrong, Mr Jones is able to find the number of the house Mr Smith lives in... Or not!

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Explore this how this program produces the sequences it does. What are you controlling when you change the values of the variables?

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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?

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

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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...