Strategies

Once you know the methods, solving Sudoku would be easy for you. Take this grid for example:

We can first check. Remember that in every 3*3 block the numbers 1-9 can only appear ONCE. In this case, the block here:

We can fill in the remaining number (7).

The rule also applies the same to every column and every row.

After this, we can use the method of scanning. Since every 3*3 block has 9 numbers that never repeats and when these blocks are put together, those numbers would also not be repeated. Thus, a pattern could be seen. For example, the no. 6 was seen in the first block in the third row, middle column, then, in the next block, 6 can’t be in the third row, nor the middle column. If the Sudoku grid you are having consists of two of the same number in three consecutive rows/columns, you can easily find out where the third same number should be put. Look at the example:

These methods can help you get most of the grids in the Sudoku. There would be one more way that you can use. Take this grid as an example:
On the grid, we can see that the arrow-pointed grids must be either 2,4 or 5. To solve this, we can use pencil marking.

Using the information we have, put the possible numbers, or “pencilmarks” on the top left corner of the grid. For the first column, because of having 5 already, cross out the possibility of 5 in the three numbers and put 2 and 4 on the top left corner. For the second column, pencilmark 2. For the third column, pencilmark 2 and 5

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Here are the combined pencilmarks. Compare them.

For the grid in the second column, 2 is the only possibility, so fill the grid with 2

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Cross out the other possibilities of 2.
Only one possibility is left for each grid, so fill those grids in with that number.