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# Solving Techniques 1 Hidden Singles

Finding the last remaining number based on already confirmed numbers is very simple and it's the most basic technique used in Sudoku.

## BOX

8's are already filled in as candidates in the G3 and F9 cells. This means that in the lower right hand box, an 8 is in the H7 cell.

## Line

In the B Line, there are no 5's. In the upper left and upper right boxes, there are already confirmed 5's, which leaves B5 and B6 as the only options. Since there is already a 5 in E5, the number 5 can't be in column 5, hence confirming that it is in B6.

## Line

Likewise, for E6, there are 2's in rows D and F and since there is a 2 in column 4, the 2 is therefore in E6, in the center block.

## The hidden singles technique is a basic method to solve Sudoku problems.

This method of eliminating potential numbers in cells for rows, columns and boxes, until the last possible number remains, is at the foundation of Sudoku and it will be used at all levels.
Most of the beginning level problems on this site can be solved, solely using this method.

## Names of cells in Sudoku

 A1 A2 A3 A4 A5 A6 A7 A8 A9 B1 B2 B3 B4 B5 B6 B7 B8 B9 C1 C2 C3 C4 C5 C6 C7 C8 C9 D1 D2 D3 D4 D5 D6 D7 D8 D9 E1 E2 E3 E4 E5 E6 E7 E8 E9 F1 F2 F3 F4 F5 F6 F7 F8 F9 G1 G2 G3 G4 G5 G6 G7 G8 G9 H1 H2 H3 H4 H5 H6 H7 H8 H9 I1 I2 I3 I4 I5 I6 I7 I8 I9