Sudoku FlowSudoku technique lessons / Hidden Quad
Lesson 14
Hidden Quad
The rule
Four numbers whose candidates together appear in only four cells of a row, column, or box claim those cells for themselves.
Step by step
- In this row, 1, 2, 3, 4 appear as candidates only in these four cells.
- These four cells must contain 1, 2, 3, 4 among them, so we can remove any other candidates from those cells.
Try it on more boards
Each board is a real puzzle from our app, at a moment where Hidden Quad applies. Find the step yourself, or tap Hint and the app's own hint walks you through it.
Want more boards like this?
We also make a Sudoku app for iPhone, iPad, Mac and Android. There are no ads in it at all, it works offline, and when you ask for a hint it shows you the technique instead of just filling in a number.
Sudoku Flow is made by Rubigo Games, the developer of the Sudoku app recommended on this site.