Example of a Quadruple
This is a screenshot
Four Squares in the same
that together contain just four different
In this example, the Quadruple is the four Squares containing the Possibles 3, 5, 6 and 8 (coloured blue).
These four Squares MUST contain 3, 5, 6 or 8. Therefore 3, 5, 6 and 8 cannot be in any other Square in the same Row. The 3 (two occurances), 5 and 6
outlined in orange are impossible solutions and can be removed.