How to Solve Sudoku: Hidden Pair

2 digits can each go only in the same 2 cells. Then the other notes in those 2 cells can be removed.

On Puzzle Lounge it appears from Hard up.

See it step by step

  1. A board full of notes. Look at row 2 (the small digits are the notes, or candidates)
  2. Only the notes in row 2 are left (the large digits are the notes)
  3. 3 and 5 can only go in these 2 cells (no other cell has a note for 3 or 5)
  4. These 2 cells are filled by 3 and 5 (3 and 5 must go somewhere in this row)
  5. So the other notes in these 2 cells can be removed (4 goes from row 2, column 9)

This is Hard No.136, partly solved.

Solve this puzzle →Print and solve →

How to find it

  1. Write out your notes (candidates).
  2. Pick a column (or row, or box) and look for a digit with only 2 places to go.
  3. If another digit can go only in the same 2 cells, remove the other notes from those 2 cells.

Things to watch

  • The 2 digits must each fit in exactly the same 2 cells and nowhere else.
  • You remove the other notes in those 2 cells, not notes in other cells. It is the opposite of the Naked Pair, so take care.
Read the full explanation

When, in a column, row or box, 2 digits can each go only in the same 2 cells, those 2 cells are filled by those 2 digits. The other candidates written in the 2 cells can be removed.

Suppose that in a row, 3 and 8 can each go only in the 2 cells A and B.

3 and 8 must both go somewhere in this row, so the 2 cells A and B are filled by 3 and 8.

So any notes in A and B other than 3 and 8 can be removed. With so many notes the pattern is hard to see, which is why it is called "hidden".

In row 2, 3 and 5 can go only at row 2, column 1 and row 2, column 9. These 2 cells are filled by 3 and 5, so the other notes (4) can be removed.

Other techniques

Hidden SingleNaked SinglePointingClaimingHidden TripleCage Combinations (Killer)Rule of 45 (Killer)Naked PairNaked 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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