LEVEL 5
Hidden Quad
Four digits occur only in the same four cells of a house.
How to find it
- Map four missing digits in a crowded house.
- Verify they are restricted to four cells.
- Keep only those four digits in the selected cells.
Logical demonstration
The violet cells represent the pattern; the gold cell represents the resulting placement or elimination. Verify every highlighted candidate belongs to the required houses before acting.
••••
Common mistakes
- Using cells that do not share the required row, column, box or peer relationship.
- Removing a candidate before confirming every occurrence in the pattern.
- Confusing a possible pattern with a completed logical proof.
GUIDED PRACTICE · EXERCISE 1 OF 3
Hidden Quad training
Identify the logically justified next action. Violet cells form the pattern and the gold cell is the proposed result.
••••
0 attempts0% accuracyIn progress mastery