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

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The clues for this Sudoku are the product of the numbers in adjacent squares.

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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...

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Given the products of adjacent cells, can you complete this Sudoku?

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Here is a Sudoku with a difference! Use information about lowest common multiples to help you solve it.

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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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Given the products of diagonally opposite cells - can you complete this Sudoku?

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Arrange the four number cards on the grid, according to the rules, to make a diagonal, vertical or horizontal line.

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Ben, Jack and Emma passed counters to each other and ended with the same number of counters. How many did they start with?

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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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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.

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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?

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Find the values of the nine letters in the sum: FOOT + BALL = GAME

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The items in the shopping basket add and multiply to give the same amount. What could their prices be?

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Mr McGregor has a magic potting shed. Overnight, the number of plants in it doubles. He'd like to put the same number of plants in each of three gardens, planting one garden each day. Can he do it?

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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

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How many solutions can you find to this sum? Each of the different letters stands for a different number.

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The letters in the following addition sum represent the digits 1 ... 9. If A=3 and D=2, what number is represented by "CAYLEY"?

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Find the smallest whole number which, when mutiplied by 7, gives a product consisting entirely of ones.

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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?

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A cinema has 100 seats. Show how it is possible to sell exactly 100 tickets and take exactly Â£100 if the prices are Â£10 for adults, 50p for pensioners and 10p for children.

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

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Can you arrange the digits 1, 1, 2, 2, 3 and 3 to make a Number Sandwich?

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This Sudoku requires you to do some working backwards before working forwards.

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Five numbers added together in pairs produce: 0, 2, 4, 4, 6, 8, 9, 11, 13, 15 What are the five numbers?

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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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In this game you are challenged to gain more columns of lily pads than your opponent.

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By selecting digits for an addition grid, what targets can you make?

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

Find out about Magic Squares in this article written for students. Why are they magic?!

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Two sudokus in one. Challenge yourself to make the necessary connections.

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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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The puzzle can be solved with the help of small clue-numbers which are either placed on the border lines between selected pairs of neighbouring squares of the grid or placed after slash marks on. . . .

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Each of the main diagonals of this sudoku must contain the numbers 1 to 9 and each rectangle width the numbers 1 to 4.

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Different combinations of the weights available allow you to make different totals. Which totals can you make?

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An investigation involving adding and subtracting sets of consecutive numbers. Lots to find out, lots to explore.

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Rather than using the numbers 1-9, this sudoku uses the nine different letters used to make the words "Advent Calendar".

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

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Use the differences to find the solution to this Sudoku.

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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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Two sudokus in one. Challenge yourself to make the necessary connections.

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This Sudoku, based on differences. Using the one clue number can you find the solution?

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A few extra challenges set by some young NRICH members.

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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.