At the moment Sudoku puzzles are very popular, people of all ages play it fanatically.
Just like the other puzzles on this site you don't need any knowledge nor calculation to solve it.

A standard Sudoku puzzle may look like this: It is a square of 9 by 9 boxes, divided (slight colour difference) in 9 sectors.
Each square should be filled with a number 1 until 9 in such a way that:
- Each number 1 upto 9 occurs exactly once in each row
- Each number 1 upto 9 occurs exactly once in each column
- Each number 1 upto 9 occurs exactly once in each sector
Some of the numbers are pre-installed in the grid, your task is to complete the matrix.
If the puzzle has been set op correctly, there should be only one way left to solve this.

How to solve a Sudoku puzzle?
There are a few different technics.

Conclusion A - "one possibility"

Have a simple start. Suppose these numbers are known: Watch the circle in the middle.
The vertical column contains all numbers except the 6.
Conclusion: The free box should be 6.

Exercise: Wich number can be found here? Which follows? And next?
When you found the correct box, the conclusion shouldn't be to difficult. This exercise also shows that one conclusion invokes the next.
Hint: choose order a, b, c, d (click here)

Conclusion B - "elimination"

Watch this example. Suppose these numbers are known: Concentrate at the circle in the middle of the top row.
Numbers 1, 2, 3, 4 are impossible, because they already occur in the top (horizontal) row.
8 and 9 won't fit either, they occur in the middle vertical column.
Even 6 and 7, they are found in the same sector.
Conclusion: only number 5 is still possible.
The majority of all sudoku puzzles can be solved with only this conclusion!!!!

Exercise: Wich number can be found here? Which nummbers follow?
It gets clearly a bit less easy... You have to find boxes where you can eliminate many nrs.
Hint: choose order a, b, c, d (click here)
A matter of art to find the first box, after some exercise you will find them more quickly.

Conclusion C - the only place

Watch here, suppose this situation: We again concentrate at the circle in the middle of the top row.
Each number is still possible in the circle, No number can be eliminated with conclusion A or B,
We only have some information about the number 4, it occurrs at some other places.
Also this sector should get a 4 somewhere...
However, not at rows 2 and 3, they are occupied.
And not at column 1 and 3 of this sector, for the same reason.
Conclusion: the cirkel is the only place for a 4 in this sector!!!

Exercise: Which numbers can be found here with conclusion C?
Solution (click here) Why? work it out yourself.
Have lots of exercises! It will make you faster and stronger.