A basic way to solve Sudoku, ideal for beginners. The essence of the technique is reflected in the name: you need to find the missing number in the block. To do this, we look:
- which values are already in the central 3x3 block: 2, 4, 6, 3 and 7;
- which numbers are missing in the block: 1, 5, 8 and 9;
- which numbers are in the row (3, 6, 7, 4);
- which numbers are in the column (8, 9, 2, 3, 1).
Using the method of elimination, we find that in the intersection cell (marked with an orange frame) the only possible digit is a five. So we write the number 5 in the cell.
Check yourself! The numbers 1, 8, and 9 cannot be used because they are already in the column, and the number 5 is neither in the column nor in the row. The Sudoku's condition that digits must not be repeated in the block, vertical, and horizontal columns is satisfied.
The "Last Free Cell", "Last Possible Number", and "Last Remaining Cell" methods are among the basic ways to solve Sudoku. Once you have mastered them, you can move on to more complicated ones.