Hidden pairs

A hidden pair is a naked pair in disguise. If two numbers can only go in the same two cells of a row, column or box, those cells must hold exactly those two numbers, so every other candidate in them can go.

How to spot it

1. Pick a unit and look for two numbers whose marks appear in only two cells, the same two for both.
2. Those two cells must hold that pair between them.
3. Remove all other candidates from those two cells.

A real example

In box 6, 3 and 9 can only go in r6c8 and r6c9. So those cells hold 3 and 9 between them, and everything else comes out: r6c8 loses 4.

Tips

• It’s easiest to spot when you have full notes in the unit.
• Hidden pairs, triples and quads all work the same way; pairs are by far the most common.

Practice on Hard puzzles