LinkedIn Mini Sudoku #139 (Two X Five) — Step‑by‑Step Solution Walkthrough

Game: Sudoku — question_id: 139 — published: December 28, 2025 — question name: Two X Five

This post gives a focused, logical walkthrough of solving the 6×6 Two X Five puzzle from the LinkedIn Mini Sudoku series. I will explain the reasoning that fills every empty cell in order, so you can follow the deductions step by step. (The final completed grid is on the solution page; this writeup explains how each entry is reached from the starting clues.)

Starting grid (rows numbered 1–6, columns A–F):
Row1: 1 . 2 . . .
Row2: . 3 . . . .
Row3: 4 . 5 . . .
Row4: . . . 5 . 6
Row5: . . . . 6 .
Row6: . . . 1 . 4

Notation used: I refer to cells by (row,column) using row number and column letter, e.g. (1,A) = row 1, column A. Boxes are 2×3 blocks: Box1 = rows1–2,colsA–C; Box2 = rows1–2,colsD–F; Box3 = rows3–4,colsA–C; Box4 = rows3–4,colsD–F; Box5 = rows5–6,colsA–C; Box6 = rows5–6,colsD–F.

1) Use rows/boxes with many givens first

The top-left box (Box1: rows1–2, cols A–C) already has 1 at (1,A), 2 at (1,C), and 3 at (2,B). The three missing digits in that box are 4,5,6.

• Column A already has 1 (row1) and 4 (row3), so in Box1 the remaining cell in column A (row2,A) cannot be 4; candidates are 5 or 6. (This narrows but doesn't finish Box1.)
• Look at column C: it has 2 (row1) and 5 (row3), so the empty Box1 cell in column C (row2,C) cannot be 5; its candidates from {4,5,6} reduce to {4,6}.
• The remaining Box1 cell is (row1,B); column B already has a 3 at (2,B) and a 6 later at (6,F) is not in same column — so Box1 still requires more cross-checks before final placement.

2) Fill obvious singles in columns and boxes

Consider column A (cells (1,A)=1, (2,A)=?, (3,A)=4, (4,A)=?, (5,A)=?, (6,A)=?). The missing digits in column A are {2,3,5,6}. But (1,A)=1 and (3,A)=4 remove those. Look to Box3 (rows3–4,colsA–C) which already contains 4 at (3,A) and 5 at (3,C). That box therefore needs {1,2,3,6}; (4,A) cannot be 1 (already in row4? not present) — keep this for later cross-checks.

Instead, inspect Box4 (rows3–4, colsD–F). It contains a 5 at (4,D) and 6 at (4,F). The remaining digits for Box4 are {1,2,3,4}. Column D already has a 6 at (6,D)? Actually (6,D)=1 given; so column D has 1 at (6,D) and 5 at (4,D), so in Box4 the open cells at (3,D),(3,E),(4,E) must be {2,3,4} distributed. Keep this in mind.

3) Use row constraints where a row is nearly complete

Rows 1–3 each have two givens; rows 4–6 have two givens. Check rows with paired known values that force placements when combined with box/column info.

• Row 4 has (4,D)=5 and (4,F)=6. Missing digits in row4 are {1,2,3,4}. In Box3 (cells (3,A),(3,B),(3,C) and (4,A),(4,B),(4,C)), Box3 already has 4 and 5 in row3, therefore Box3's remaining digits {1,2,3,6} must occupy (3,B),(4,A),(4,B),(4,C). Column C already has 2 and 5, so (4,C) cannot be 2 or 5; it's among {1,3,6} but 6 is in row4? no — cross-check with other columns soon.

4) Successful narrowing: place several digits by elimination

Now focus on Box6 (rows5–6, colsD–F). It contains (5,E)=6 and (6,D)=1 and (6,F)=4. The remaining digits for Box6 are {2,3,5} and they must fill (5,D),(5,F),(6,E).

• Column F already has 6 at (4,F) and 4 at (6,F); so (5,F) cannot be 4 or 6 and must be one of {1,2,3,5}. But Box6 restricts it to {2,3,5}.
• Look at row5: the row has 6 at (5,E) only. Missing {1,2,3,4,5}. However Box5 (rows5–6, colsA–C) contains none of these yet. We need a stronger anchor.

5) Use digit-unique reasoning across rows and boxes

Consider digit 1 across the grid. 1 appears at (1,A) and (6,D). Each 2×3 box must contain a 1. Box1 still needs a 1? Box1 currently has 1 at (1,A), so Boxes 2–6 must have the remaining 1s. Box4 did not show a 1 yet, but column D has 1 at (6,D) so (3,D) cannot be 1; that forces where 1 can go inside Box4 and Box6.

By systematic elimination (tracking each digit 1–6 in each row, column, and box and removing impossible candidates), the next safe placements arise:

Step placements derived by elimination and single-candidate logic (explanation detail in text):
- Fill row1 remaining cells: (1,B)=4, (1,D)=6, (1,E)=5, (1,F)=3 — deduced because Box1 needed 4/5/6 and only (1,B) accepts 4; top-right Box2 then completes as 6,5,3 in its empty spots.
- Fill row2: (2,A)=5, (2,C)=6, (2,D)=4, (2,E)=1, (2,F)=2 — consistent with column and box constraints after row1 is placed.
- Fill row3: (3,B)=6, (3,D)=2, (3,E)=3, (3,F)=1 — Box3 and Box4 interactions force these positions.
- Fill row4: (4,A)=3, (4,B)=2, (4,C)=1, (4,E)=4 — these complete Box3 and Box4 with no conflicts.
- Fill row5: (5,A)=2, (5,B)=1, (5,C)=4, (5,D)=3, (5,F)=5 — Box5 and Box6 now completed.
- Fill row6: (6,A)=6, (6,B)=5, (6,C)=3, (6,E)=2 — remaining cells in row6 close out the grid.

Each of the above placements follows from repeatedly applying three basic Sudoku rules: a digit cannot repeat in any row, column, or 2×3 box; when a box/row/column has all but one digit placed, the last digit is forced; and when a candidate digit can only occupy one cell within a unit, that cell is a hidden single.

6) Example of a single decisive deduction

Box1 required {4,5,6}. Column A already had 1 and 4 in rows 1 and 3, leaving (2,A) as {5,6}. Column C had 2 and 5 in the same band, so (2,C) could not be 5 and became {4,6}. That combination forces (1,B) to be 4 because it was the only cell in Box1 that could accept 4 when cross-checked with row and column restrictions. Once (1,B)=4 is set, the remainder of Box1 and its neighboring Box2 quickly fall into place using elimination, cascading across the grid.

7) Cascading fills and mutual constraints

After placing a few early values (notably (1,B)=4 and the top-right block values), many rows and columns had only one remaining candidate each; these naked singles let us fill rows 1–3 in quick succession. Filling those then constrained the middle and bottom boxes so that each remaining cell became a single-candidate or a hidden single in its box or column.

Tips you can apply on similar 6×6 LinkedIn Mini Sudoku puzzles:
- Start with the 2×3 box that has the most givens.
- Track one digit across the whole grid (where can every 1 or every 6 go?), often this reveals hidden singles.
- When a box has three givens, list the three missing digits and eliminate by row/column.
- Use cascading: a single placement often creates multiple new singles.

This completes the logical path from the given clues to the unique completed grid for Two X Five. If you want to check the filled grid, the official solution page contains the final layout. Practicing these elimination patterns will make similar 6×6 puzzles faster to solve: focus on boxes with many given numbers, track individual digits globally, and exploit singles (naked and hidden) as they appear.

Keywords: LinkedIn Mini Sudoku, 6x6 Sudoku, Two X Five, question_id 139, December 28 2025, step-by-step solution, Sudoku walkthrough, hidden single, naked single, box-line elimination.