- The puzzle is a 4x4 grid, which means each row, column, and 2x2 subgrid must contain exactly one of each color: blue, green, orange, and red.
- Start with the top row. It already has blue and green in the second and third cells. The first and fourth cells must be orange and red. Look at the first column: it has an orange in the second row, so the top-left cell cannot be orange; it must be red. Therefore, the top-right cell must be orange.
- Move to the second row. It has orange in the first cell and blue in the third cell. The second and fourth cells must be green and red. Look at the second column: it has blue in the first row and red in the third row. So the second cell of row two must be green (since red is already in that column). Then the fourth cell of row two must be red.
- Now examine the third row. It has red in the second cell and orange in the third cell. The first and fourth cells must be blue and green. Look at the first column: it has red in row one and orange in row two, so the third row, first cell can be blue or green. But look at the fourth column: it has orange in row one and red in row two, so the third row, fourth cell must be either blue or green. Also, the third row’s 2x2 subgrid (bottom-left) already has red and orange, so it needs blue and green. Check the fourth column: it has orange (row1), red (row2), and will have something in row3 and row4. The bottom-right 2x2 subgrid has orange and red in row4, so row3, col4 must be blue or green. Let’s look at column 4: if we put green in row3, col4, then row4, col4 must be blue. But row4, col3 is red, so row4, col4 can be blue. That works. So set row3, col4 to green. Then row3, col1 must be blue (to complete the row and the bottom-left 2x2 subgrid).
- Finally, the fourth row. It has orange in the second cell and red in the third cell. The first and fourth cells must be blue and green. Look at column 1: it has red (row1), orange (row2), blue (row3), so row4, col1 must be green. Then row4, col4 must be blue.
Final grid:
Row 1: Red, Blue, Green, Orange
Row 2: Orange, Green, Blue, Red
Row 3: Blue, Red, Orange, Green
Row 4: Green, Orange, Red, Blue
Parent Tip: Review the logic above to help your child master the concept of printable junior sudoku.
