How to Solve Sudoku: Naked Pair

2 cells have only the same 2 digits in their notes. Then those 2 digits can be removed from the other cells of that column, row or box.

Also called simply a pair. On Puzzle Lounge it appears from Hard up.

See it step by step

  1. A board full of notes. Look at row 6 (the small digits are the notes, or candidates)
  2. Only the notes in row 6 are left (the large digits are the notes)
  3. 2 cells with only 3 and 4 in their notes
  4. 3 and 4 can only go in these 2 ways (each puts one in each of the 2 cells)
  5. In every case, 3 and 4 are used up by these 2 cells (they cannot go in other cells of row 6)
  6. So the other 3s and 4s can be removed (3 and 4 go from row 6, column 2)

This is Hard No.30, partly solved.

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How to find it

  1. Write out all your notes (candidates).
  2. Find a cell with only 2 candidates, then see whether another cell in the same column, row or box has exactly the same 2.
  3. If you find one, remove those 2 digits from the other cells of that column (or row, or box).

Things to watch

  • The candidates must be "the same 2 and no others". If either cell still has a third candidate, it does not work.
  • You can only remove them within a column, row or box that contains both of the 2 cells.
Read the full explanation

When 2 cells in a column, row or box have the same 2 digits as their only candidates, those 2 digits are used up by those 2 cells. Those 2 digits can be removed from the other cells.

Suppose cells A and B both have only {3, 7} as candidates. If A is 3, B is 7; if A is 7, B is 3. Either way, 3 and 7 go in A and B.

So neither 3 nor 7 can go in the other cells of any column (or row, or box) that contains both A and B. 3 and 7 can be removed from those cells' notes.

In row 6, row 6, column 3 is {3, 4} and row 6, column 9 is {3, 4}. Together that is just the 2 digits 3 and 4, so these 2 cells use them up. So 3 and 4 can be removed from the candidates at row 6, column 2, in the same row.

Other techniques

Hidden SingleNaked SinglePointingClaimingHidden PairHidden TripleCage Combinations (Killer)Rule of 45 (Killer)Naked TripleX-WingXY-WingSwordfishSkyscraper2-String KiteXYZ-WingW-WingJellyfish

For the basics and how to use notes, see how to solve sudoku, with tips. If you get stuck, the game's hints guide you step by step, starting with where to look.

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