Naked Quad
Pretty similar to the “Naked Triple,” but based on four candidates instead of three, so it’s a bit harder to spot
- Look at this example
- The highlighted cells contain only values 2, 4, 6, and 8
- That means 2, 4, 6, and 8 can’t appear in other cells of the unit and can be deleted
- A Naked Quad can also be found in a column or a row
