Kendoku is just another type of Sudoku. Sudoku with a twist!

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**How to Solve a Kendoku Puzzle**

Kendoku or KenKen looks like a basic Sudoku grid, its dimensions ranging from 3×3 to 9×9 cells. The aim of the game is to fill the cells with numbers, making sure the same digit does not appear twice in the same row or column. For a 4×4 grid you have to work with numbers from 1 to 4, while for a 9×9 you will have to use all the digits from 1 to 9. So far, so good, your basic Sudoku puzzle. However, here comes the twist.

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**What are Kendoku Puzzle Cages?**

Every grid contains a number of so-called cages, that is heavily outlined groups of cells and the numbers in each of them must produce a certain magic numbers. The first cell in a cage will have inscribed in the upper left corner the target number and the mathematical operation to be used to reach that number. Most magic number puzzles only use addition, but in Kendoku you might have to use subtraction, multiplication or division to reach that target number. Each cage has its own mathematical operation so it’s quite possible to have to use all four of them while solving a grid. More advanced Kendoku puzzles may include other types of complex operations or use negative numbers.

You can have a number repeated in a cell, as long as they are not on the same row or column.

In some cases, no operation is specified so the player is free to reach the target number anyway he can.

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**History of the Kendoku Puzzle**

Kendoku was invented in 2004 by a Japanese math teacher named Tetsuya Miyamoto, who was trying to develop a fun educational game. The name of the game comes from the Japanese term for cleverness. The new Japanese puzzle gained international fame in 2008 when British newspaper ‘The Times’ first published a Kendoku grid. At present, hundreds of papers in the US and Europe regularly publish Kendoku, and, of course, such puzzles can be found on many websites.

Since its a puzzle with an outstanding educational value, starting 2010 there have been national Kendoku championships, usually held in New York, as well as international competitions open to students of all levels.