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Hidden Singles

Hidden singles are the simplest an most commonly used of the major sudoku techniques. Simply stated, if there is only one empty cell within a group (row, column or box) where a digit can go, then it must go there. An example of this technique is shown below:

In this example, the red cell must be a "7". This is because, on the row below the red cell, there is already a "7" (highlighted in orange) and thus there is only one place in the box left where a "7" can go. Below are two more examples.

In the first of these examples, taken from earlier in the same game, the cell highlighted in red must be a "2", because of the two "2"s highlighted in yellow. In the second example, taken from even earlier in the game, the red cell must be a "6", because all other possible locations for a "6" in the middle box are eliminated by the orange "6"s.

Once you have mastered the hidden single technique, you can solve all "Very Easy" and "Easy" sudokus in Puzzle Tiger.

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