Hidden Pairs / Triples / Quads

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Hidden Pairs / Triples / Quads

What It Is

Hidden subsets are numbers confined to the same limited cells in a unit—two numbers in two cells (pair), three in three cells (triple), four in four cells. Remove other candidates from those cells to expose the locked set.

When to Use

Mid-game with many pencil marks; when naked subsets are exhausted and you need to simplify dense candidate lists.

How to Apply (Step-by-Step)

  1. Survey a unit’s candidates: list where each missing number could go in a row/column/box.
  2. Find confined candidates: look for numbers limited to the same cells (two numbers to two cells, etc.).
  3. Confirm exclusivity: ensure no other cells hold those candidates.
  4. Eliminate other candidates from those cells: leave only the hidden set.
  5. Repeat for triples/quads.

If digits 2 and 4 only appear in two cells of a column, erase all other notes from those cells—revealing a hidden pair that simplifies the unit.

See also

Scanning / Cross-Hatching Single Candidate (Naked Single) Single Position (Hidden Single) Naked Pairs / Triples / Quads Hidden Pairs / Triples / Quads Pointing Pairs / Triples (Locked Candidates Type 1) Box–Line Reduction (Locked Candidates Type 2) X-Wing Swordfish Jellyfish XY-Wing XYZ-Wing W-Wing Alternating Inference Chains (AICs) Forcing Chains / Forcing Nets Nishio Coloring Multi-Coloring Uniqueness Techniques (Unique Rectangle etc.) Fish Variants (Finned X-Wing, Sashimi etc.) ALS Techniques (ALS-XZ, ALS Chains) Sue de Coq Pattern Overlay / Template Method
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