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Sudoku Rules

A brief guide

A Sudoku is a logic puzzle, there is no guessing involved, there is no maths involved, it is a pure logic puzzle.
This is an example of a starting grid for Sudoku - there is always some numbers that are given to you to start with. The more numbers you are given to start with, the easier the puzzle (normally).
There are three rules to Sudoku,
Each column must contain the numbers 1-9 once, and only once. The highlighted column already contains the numbers 5 and 7, you need to work out where the numbers 1, 2, 3, 4, 6, 8, and 9 need to go.
Each row must also contain the numbers 1-9 once, and only once. The highlighted row already contains the number 4, you need to work out where the numbers 1, 2, 3, 5, 6, 7, 8, and 9 need to go.
Each 3x3 region must contain the numbers 1-9 once, and only once. The highlighted 3x3 box already contains the numbers 2, 4, 6, and 7, you need to work out where the numbers 1, 3, 5, 8, and 9 need to go.
The easiest way to start is to look for cells where there is only one possible candidate. We know the bottom-left 3x3 region must contain the number 5 somewhere, but we don't know where. We also know that each row and column can only contain the number 5 once. This means we can eliminate all of the cells in that bottom-left square, apart from one. We can write in a '5' for the highlighted square.
This is a great technique to start with Sudoku puzzles.
The highlighted cell is another cell that we can fill right away. We can look at the numbers already in that column, row and 3x3 region, and by a process of elimination, work out what the highlighted cell should be.
That column already contains 2, 3, 4, 6 and 7. That row already contains 5, 6 and 8. That 3x3 region already contains 6 and 9. We know the highlighted cell can't be any of these numbers, because we can only have one of each number in each column, row, and 3x3 region. The highlighted cell can't be any of 2, 3, 4, 5, 6, 7, or 9. This leaves us with just the number 1!
I have highlighted three squares that you can fill in using the two techniques you have just learnt.
The rest of the puzzle can be solved using the two techniques you have just learnt.
All of our puzzles are graded easy, medium or hard. Go to the archive page and find an easy puzzle to start with!