GridWits
Easy tier Technique 2 of 20 Used by Smart Hint

Hidden Single

A value has only one possible cell left in this row or column, even though that cell has other candidates too.

How it works

  1. 1Columns 1, 3 and 4 already have their 1 somewhere lower down.
  2. 2So in the top row, the only cell that can still take a 1 is the second one — even though that cell has other candidates too.
  3. 3That is what makes it HIDDEN: you find it by asking where a number can go, not by asking what a cell can hold.
2 3 4 1 2 3 4 2 3 4 2 3 4 1 1 1
  • Number this technique proves
  • Cells read together — The connecting line shows which cells combine to make the deduction.
  • Conclusion — The coloured candidate, or the final arrow when it lands outside the pattern, shows the result.
Next in the ladder Inequality Bound →

Across a sign, the smaller cell can't reach the larger cell's biggest candidate, and the larger cell can't drop to the smaller cell's smallest.