Solving Classic Sudoku: 'Naked Pairs/Naked Triplets'

This is an advanced technique of solving a sudoku. It is hard to use this technique, but very useful! If there are two (three) cells of a row/column which can take any one number of a pair (triplet) of numbers, then that pair (triplet) of numbers cannot be placed in any other cell of that row/column.

Take a look at this Classic Sudoku below. Observe the 2nd, 4th and 8th columns, alongwith the 1st row.


The 2nd and 4th columns have two empty cells each for '4' and '6'. The 8th column has three empty cells for '4', '6' and '7'.


Observe R1C2, R1C4 and R1C8.


Since R1C2 and R1C4 are two cells which have to be the pair '4' and '6', they cannot be placed in any other cell of the 1st row. Hence, R1C8 cannot be '4', nor '6', and it has to be '7'.

Other Solving Techniques