Box-Line Reduction
IntermediateUsed at: Hard
When a digit in a row (or column) appears only in one box, it can be eliminated from that box's other rows (or columns).
Box-Line Reduction — Explained
Box-Line Reduction is the reverse of Pointing Pair. When a digit in a row appears only in one box, it can be eliminated from other rows in that box.
When to Use
Paired with Pointing Pair, essential for intermediate to advanced puzzles.
Common Mistakes
Confusing Box-Line Reduction with Pointing Pair. Remember: Pointing Pair is box→line, BLR is line→box.
Tips
Scan each row for digits concentrated in a single box. Harder to spot than Pointing Pair.
Box-Line Reduction Steps
1
Find a digit in a line
Find a digit that, within a row or column, only appears in one box.
2
Check the box
Look at other rows/columns in that box for the same candidate.
3
Apply elimination
Eliminate the digit from other rows/columns in that box.