Based on the analysis of the 4x4 grid, the solution is derived from a clear pattern:
each of the four 2x2 sub-grids must contain the numbers 1, 2, 3, and 4 exactly once.
This is similar to a Sudoku puzzle but with 2x2 blocks instead of 3x3.
Here is the step-by-step solution for each sub-grid:
1.
Top-Left Sub-Grid (already complete):
* This block already contains all numbers 1-4: 4, 3 in the top row, and 1, 2 in the bottom row.
*
Final state: `[[4, 3], [1, 2]]`
2.
Top-Right Sub-Grid:
* It has a '3' in the bottom-left cell.
* To complete the set {1, 2, 3, 4}, it needs the numbers 1, 2, and 4.
* There are no other constraints from the given image, so there are multiple valid ways to arrange these numbers. A logical arrangement would be to place them sequentially.
*
One possible solution: Place 1 and 2 in the top row, and 4 in the bottom-right cell.
*
Final state: `[[1, 2], [3, 4]]`
3.
Bottom-Left Sub-Grid:
* It has a '2' in the bottom-left cell and a '1' in the bottom-right cell.
* To complete the set {1, 2, 3, 4}, it needs the numbers 3 and 4.
* These must go in the two empty cells in the top row.
*
One possible solution: Place 3 in the top-left and 4 in the top-right.
*
Final state: `[[3, 4], [2, 1]]`
4.
Bottom-Right Sub-Grid:
* It has a '2' in the top-left cell.
* To complete the set {1, 2, 3, 4}, it needs the numbers 1, 3, and 4.
* Again, with no other constraints, we can arrange them logically.
*
One possible solution: Place 1 and 3 in the top row, and 4 in the bottom-right cell.
*
Final state: `[[2, 1], [3, 4]]`
Final Answer:
By applying the rule that each 2x2 sub-grid must contain the numbers 1, 2, 3, and 4 exactly once, the completed grid is:
```
4 3 | 1 2
1 2 | 3 4
----+----
3 4 | 2 1
2 1 | 3 4
```
Parent Tip: Review the logic above to help your child master the concept of printable sudoku puzzles for beginners.
