Here is the naked Triple move:
- Code: Select all
*---------------------------------------------------------------*
| 2 9 5 | 7 34 134 | 8 6 134 |
| 47 3 1 | 8 6 5 | 9 2 47 |
| 8 47 6 | 1249 2349 12349 | 45 134 13457 |
|--------------------+--------------------+---------------------|
| 3-49 18-4 7 |*249 5 *249 |*24 138-49 6 |
| 469 146 29 | 3 8 7 | 245 149 145 |
| 5 48 2389 | 249 1 6 | 7 3489 348 |
|--------------------+--------------------+---------------------|
| 367 678 38 | 5 2347 234 | 1 48 9 |
| 179 2 89 | 6 479 149 | 3 5 48 |
| 139 5 4 | 19 39 8 | 6 7 2 |
*---------------------------------------------------------------*
You can see that the three cells marked * only contain three different digits : 2, 4 and 9. So these 3 digits must occupy these three cells in some order (it doesn't matter which order).
The important point is that any cell that can see all of these three cells can have 2, 4 and 9 removed. In this case it apples to any cell in Row 4 except for the three * cells, 5 eliminations in this case.
The logic underlying these eliminations is that, if any other cell in Row 4 solved to 2, 4, or 9 there wouldn't be enough digits to fill the three * cells, and at least one of them would be empty - that's bad !
Note that the three cells must be in the same row, column or box for this move to apply.
Also, here is the puzzle in . line format : 2957..86..3186592.8.6........7.5...6...387...5...167.....5..1.9.2.6..35..54..8672
Links to good teaching sites that explain the naked triple move can be found
here and
here.
Leren
PS thanks to Jason for showing me how to change the URL gobbldegook into nice labels. Only took me 4 years to get around to asking him how to do it but better late than never.