Remote Pairs
A chain of bi-value cells all sharing the same pair {X,Y}. Alternating X/Y along the chain means the two ends are opposite, so any cell seeing both loses both candidates.
Four bi-value cells, all showing 2 and 7, link together: each shares a house with the next.
How to spot it
- 1Link bi-value {X,Y} cells that see each other into a chain.
- 2Colour them alternately X and Y along the chain.
- 3Any cell that sees both an X-end and a Y-end can't be X or Y.
When to use
When several identical bi-value cells thread across the grid.
Common mistake
Breaking the chain by including a cell with a third candidate.
Worked Example
A remote pair is a chain of cells that all show the exact same two candidates, {X,Y}, each one seeing the next in the chain. Since every cell in the chain is bi-value, the values have to alternate: if the first cell is X, the next must be Y (they share a house), the one after that X again, and so on down the chain.
Follow that alternation to the far end, and the two endpoints always land on opposite values from each other, regardless of which way the whole chain actually resolves. Any cell that sees both endpoints therefore can't be X or Y, so both candidates can be removed from it.