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Improve your Sudoku Skills (Beginner)
Getting into Puzzle Mode
This tutorial is primarily for beginner solvers who haven't done many sudokus and would like to learn a systematic approach to solving sudokus. If you feel confident with this skills, you can try taking a look at the intermediate or advanced hub in this three part series.
These rules are applied the most often out of the various sudoku skills that are used. In particular, the beginner skills account for most of the steps in any sudoku including the intermediate and advanced sudokus. Thus, it is a good idea to master these skills before you try the harder tricks.
(1) Last Square
This is the most standard rule, and most beginners are often introduced to sudoku with this rule. As it is the simplest rule, it is also the most common rule, which means it should be applied first out of all the rules. The rule occurs when you have a row, column or box that already has eight solved squares.
In picture A (to the right), 'Ba' is the lastsquare in row B. All we have to do is find out which number is missing in that row (4) to solve that square.
This is another standard rule, and is quite common. Row, column, and box information can together provide the clues necessary to narrow down the possibility to one number for a given square.
In the picture to the right (picture B), we observe 'Da.' The row information (row D) tells us that only 3 & 7 are possibilities. The column information (column a) tells us that only 6, 7, 9 are possibilities. The only possibility in common is 7, so that number must go in that square.
This rule, allows us to exclude particular choices in some square where there are only a few possibilities.
Example: In picture C, we look at the crosshair centered at 'Ic,' and see that either a 1 or 3 can go in column c by looking at the other numbers in the column. However, row I already has a 3 in the row, which means it 'Ic' cannot be another 3, so it must be a 1. This means 'Ac' is a 3.
(4) Slicing and Slotting
In this technique, we take groups of two or three rows or column working methodically through the whole grid by looking for possible slots for 1s then 2s, 3s, etc.
In picture D, we first look at the top three rows for 1. 'Ae' and 'Ca' are 1s, and there is no 1 in row B, so we can look for an adequate spot for 1 in row B amongst the four open slots. It can't be in the same region as the 1 in 'Ae' however, so three spots are eliminated as choices. Thus 1 must go in 'Bi.' We can use the same strategy for rows D, E, and F. D only has two empty spots. We can eliminate 'Di' because there is already a 1 in region 'Di.' Thus there must be a 1 in square 'Dc.'
Have fun applying these tricks! Once you feel confident using them, you can move on in to the intermediate skills in this series.