Example of a Two Squares

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This is a version 14.0 screenshot

Two Squares:

Taking advantage of 'The 45 Rule' (every Row, Column and Box consists of the numbers 1 to 9 and so must sum to 45), this analysis looks for a set of Rows, Columns or Boxes that is missing two squares (or has two extra squares). The total of these two squares can then be determined, causing some of the possibles in the two squares to be impossible solutions.

In this example, the Killer Groups outlined in red form a set consisting of the bottom Row plus the two squares G9, and H9. The set of Killer Groups sums to 60. Since the bottom Row must sum to 45 (the 45 rule), the two squares must sum to 15, causing a number of impossible solutions (outlined in orange) which can be removed.




Second Example of a Two Squares

Screenshot
This is a version 14.0 screenshot

Two Squares:

In this second example, the Killer Groups outlined in red form a set consisting of the bottom two Rows plus the three squares G5, and G9. The set of Killer Groups sums to 100. Since the bottom two Rows most sum to 90 (2 X the 45 rule), the two squares must sum to 10, causing a number of impossible solutions (outlined in orange) which can be removed.




Third Example of a Two Squares

Screenshot
This is a version 14.0 screenshot

Two Squares:

In this third example, the Killer Groups outlined in red form a set consisting of the bottom-right and the bottom-middle Boxes, minus the two squares G8, and G9. The set of Killer Groups sums to 86. Since the two Boxes sum to 90 (2 X the 45 rule), the two squares must sum to 4, causing a number of impossible solutions (outlined in orange) which can be removed.