What are pairs and triples in Queens?

A pair is two colours whose open tiles all lie in the same two rows (or the same two columns). Those two colours will take both of those lines' queens, one each, so every other tile in the two lines can be crossed out. A triple is the same with three colours in three lines. It works the other way round too: two rows whose open tiles are only two colours claim both colours.

A pair

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The pearl colour and the rose colour only have open tiles in column 3 and column 4. Two colours in two lines: between them they will use every queen those lines have, so every other tile in column 3 and column 4 can be crossed out.

A triple

The emerald colour, the topaz colour and the lagoon colour only have open tiles in column 2, column 3 and column 1. Three colours in three lines: between them they will use every queen those lines have, so every other tile in column 2, column 3 and column 1 can be crossed out.

Why it works

Count the queens. Two colours need two queens. If the only places for them are inside two lines, those two queens are the two queens those lines are allowed. There is no queen left over for any other colour in those lines.

How to spot it

• Look for two small colours stacked in the same two columns, or lying side by side in the same two rows, often along an edge.
• For each pair of neighbouring rows, count the colours that are completely inside them. If it's two, you have a pair.
• Only hunt for triples once pairs are exhausted. They are rare on boards smaller than 8×8.

Related techniques

A pair is the two-colour version of a colour trapped in one line. When counting doesn't help, try the no-room test.