One of the things I that drove me crazy about Sudoku is how difficult it is to return to a puzzle if you get interupted. This system allows you to walk away from a puzzle at any time and return exactly where you left off.
Step 1: What You Need to Begin
1. A sudoku puzzle. I enlarged this one (which was the puzzle that appeared on Sudoku.com on July 8, 2006.) to make photography easier. I find this system works better on larger puzzles.
2. A pencil, Not a pen. A pencil.
3. An eraser.
Step 2: Fill in the "Missing Grid"
Enter the numbers 1 through 9 in a "tic-tac-toe" pattern in every blank box.
Step 3: Erase "Across"
So the first number (in the upper right corner) is a "6". Erase every other "6" in that row. Once you have completed the erasing, draw a line across the top of the number to indicate that you have cleared out that line.
Step 4: Erase Down
Step 5: Erase "All Around"
Now you have eliminated all the sixes from all the other blocks. That indicates that a Six canot appear in any of those blocks.
Keep going, repeat those same three steps for all the other pre-printed numbers in the puzzle.
Step 6: Repeat for All the Pre-printed Numbers
Let's see what the result of all that erasing was.
Step 7: Locate Answers
Write that number large in the block, then treat it like a preprinted number. Eliminate all the across, down and around numbers as you have already done so many times before.
In this image, the red pen points point to all the answers that were provided just by doing the initial erasing.
We have not yet begun to think!
Step 8: Other Kinds of Eliminations.
First look down each column. If you find a number that only appears in one block in a column. That is the answer for that block.
In this picture, the pen point points to a three. That is the only three in that column, so that must be where it goes.
Write it large, then treat it like a pre-printed number. See ... this isn't thinking. This is EASY.
Step 9: Look Around a Quadrant.
If you've looked across the columns, and across the rows and there are all duplicates, then look in the group. If there is one number in the group that only appears in one block, then it's your answer.
See... There is no guessing in Sudoku. One of these situations has to occur. You just need to find them.
IN this picture the 5 only appears in one block in the group. It goes there.
Write it big, then treat it like a pre-printed number.
See where we're going, here?
Step 10: Lather, Rinse Repeat.
Remember to draw those lines and circles in case you get interrupted.
Eventually you will solve the puzzle.
Compare our solution to the "Official Solution" found on the Sudoku.com site. See? A perfect match.
And you thought Sudoku was hard.
It's so easy, you don't even have to think!