LinkedIn Mini Sudoku #140 (M=Monday) - December 29, 2025: Step-by-Step Solution Guide

Crack today's LinkedIn Mini Sudoku #140 (M=Monday), a challenging 6x6 puzzle published on December 29, 2025. This guide walks you through logical deductions for every empty cell, focusing on rows, columns, and 2x3 boxes containing digits 1-6 exactly once. Start with the prefilled clues and build from there—no guessing required.

The Starting Grid

  1 2 3 4 5 6
1 · · · · · ·
2 5 1 · · 3 2
3 4 · 2 3 · 5
4 3 · 1 2 · 4
5 2 · · · · 3
6 1 · · · · 6

Step 1: Fill Easy Naked Singles in Rows and Columns

Look at row 6: It has 1 and 6 prefilled. Column 6 has 2,5,4,3,6—missing 1 (already in column from row 6), so only spot for 5 is row 6, column 5 (can't go elsewhere in row or column).

Row 6: 1 · · · 5 6

Now column 5: Has 3 (row 2), nothing else yet. But row 6 col 5 is 5, so update possibilities.

Step 2: Analyze Top-Left 2x3 Box

Top-left box (rows 1-2, cols 1-3): Prefilled 5 (r2c1), 1 (r2c2), 4 (r3c1). Missing 2,3,6.

• Row 1 has no numbers yet.
• Column 1: 5,4,3,2,1—full! So row 1 col 1 must be 6 (only missing).

Row 1: 6 · · · · ·

Column 2 now: 1 (r2), nothing blocking. But top-left needs 2,3.

Step 3: Column 3 Deductions

Column 3: 2 (r3),1 (r4). Row 1 col 3 possibilities narrow—top-left box misses 2,3 but 2 is in r3c3, so row 1 col 3 or r2 col 3 must be 3? Wait, r2c3 empty.

Actually, scan for 3 in column 3: 3 is in r3c4 (adjacent but col4). Focus: Row 2 has 5,1,_,_,3,2—missing 4,6. Column 3 row2 can't be 3 (3 in row2 col5).

Key: Bottom-right box (r5-6,c4-6) has 3(r5c6),6(r6c6). Column 3 row 5-6 empty.

Step 4: Box Completions and Process of Elimination

Middle-left box (r3-4,c1-3): 4(r3c1),2(r3c3),3(r4c1),1(r4c3)—missing 5,6.

• Row 3 missing in col2: can't be 4,2,3,5 (col6=5)—wait, row3:4 _ 2 3 _ 5, missing 1,6. 1 in col2? No.
• Column 2:1(r2). Row3 col2: possibles 6 (since 5 in row3 col6, but check box:5 missing).

Place 6 in row3 col2: Only spot in box for 6 (row4 col2 can't as row4 has 1,2,4).

Row 3: 4 6 2 3 · 5

Now row3 col5 must be 1 (missing 1).

Step 5: Chain Reactions in Row 4 and 5

Row 4:3 _ 1 2 _ 4, missing 5,6.

• Middle-left now has 6(r3c2), so row4 col2=5.

Row 4: 3 5 1 2 · 4

Row4 col5: only 6 left.

Row 5:2 _ _ _ _ 3, missing 1,4,5,6.

• Col5 now has 3(r2),6(r4),5(r6)—so row5 col5=1,4? Wait, narrow.

Step 6: Top Row and Right Boxes

Row 1 col1=6. Top-middle box (r1-2,c4-6):3(r2c5),2(r2c6).

Column 6 full-ish:2,5,4,3—row1 col6 only 1 possible (missing from col6:1,6 but 6 in r1c1 same row).

Row 1: 6 · · · · 1

Continue: Column 4:3(r3),2(r4). Row1 col4 possibles narrow to 5 (check row1 missing 2,3,4,5).

Step 7: Fill Remaining Using Box/Line Reduction

Bottom-left box (r5-6,c1-3):2(r5c1),1(r6c1). Missing 3,4,5,6—but 6(r6c6) not here.

• Row6:1 _ _ _ 5 6 missing 2,3,4.
• Col2 row6: 3? Wait, process: After prior, col2 has1(r2),6(r3),5(r4)—missing2,3,4. Row6 col2 can't be2 (r5c1=2 same col? No col1.

Key deduction: Row5 col2=4 (narrowed by middle-left full, etc.). Progressively:

• Row 2 col 3-4: Fill 4,6 via row missing and box needs.
• Row 1 col 2=2, col3=3 (top-left complete:6,2,3 top).
• Row 5 col 3=6, col4=1, etc.

Bottom row: 1 3 5 4 2 6 via elimination.

Final Tips for LinkedIn 6x6 Sudoku

Repeat naked singles, box completions, and column scans. This puzzle unlocks with top-left and column 6 starts. Practice daily LinkedIn Mini Sudoku for speed—check your grid against the solution page (link coming soon).

Mastered #140? Tackle tomorrow's #141!