Hidden Quadruple

Working with Candidates10 / 32

Four digits that fit nowhere but the same four cells.

Four digits of a unit whose remaining homes all fall within the same four cells reserve those cells completely — the hidden pair and triple logic, one final size up.

It's the rarest of the subsets and the best camouflaged: none of the four digits needs to appear in all four cells, and the cells usually bristle with unrelated pencil marks that can now be erased.

See it in action

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Step 1 of 4

The setup

Chart where each digit of the unit can still go. Collect digits with at most four possible cells and look for four of them whose cells pool into a set of exactly four. Step through this real position to see it happen.

Practice

Find the hidden quadruple and strip the foreign candidates from its four cells.

Drill 1 of 29

Tap a cell, then the candidate digit you want to remove.