Medium XV Sudoku

X marks cells that sum to 10; V marks cells that sum to 5. All unmarked adjacent pairs must not sum to 5 or 10.

Easy Medium Hard Expert

XV Sudoku at medium difficulty. The negative constraint — unmarked pairs cannot sum to 5 or 10 — becomes as important as the X and V markers themselves.

3
7
6
2
6
6
3
9
2
4
6
1
4
9
2
4
7
8
2
5
6
2
1
8
2
3
9
4
7
8
1
8
V V X X X X V X X X X X X X V V X X X X X V X X X X X V X V X X X
Mistakes
0/3
Score
-
Time
00:00
Try Hard XV Sudoku →
Progress0%

What is XV Sudoku?

Difficulty
★★★☆☆
3/5
Constraint Type
Cell Relationships
Typical Givens
18–24
Avg. Solve (Medium)
18 min

Solving Techniques for Medium Level

Technique Description Level
Negative Constraint Where no X or V appears between adjacent cells, their sum is neither 10 nor 5. This eliminates (1,9), (2,8), (3,7), (4,6) for X and (1,4), (2,3) for V. Beginner
Sum Pair Enumeration List all digit pairs that sum to 10 (for X) or 5 (for V), then use row/column placement to identify which pair must occupy each marked pair. Beginner
Marker Chain Logic Multiple consecutive X and V markers in a row form a sum chain — enumerate valid assignments for the entire chain simultaneously. Intermediate

Master these, then take on Hard XV Sudoku to learn Advanced techniques.

Techniques to Master at Medium

  • Hidden Singles technique — Where can 5 go? Never on a V, and on an X only opposite another 5 — impossible. The digit 5 avoids every marker, making its hidden singles the fastest finds in XV.
  • Obvious Pairs technique — An X pair narrowed to {4,6} or {2,8} is a ready-made pair for its row and box, and the marker even survives once one digit lands — the partner is forced.

Average Solve Time by Difficulty

Easy
8 min
Medium
18 min
Hard
35 min
Expert
62 min
Want a full walkthrough of rules, strategies, and solving steps? How to Play XV Sudoku →

Related Variants

Kropki Sudoku

Swaps sum markers for difference and ratio dots — the same marked-pair-plus-negative-constraint solving rhythm.

Consecutive Sudoku

A single-marker version of the same idea: every consecutive neighbour pair is flagged, and silence is information.

Greater Than Sudoku

Adjacent cells related by order instead of sums — chains of inequalities replace chains of X and V markers.

Frequently Asked Questions — Medium XV Sudoku

What techniques are needed for medium XV Sudoku?
Medium XV Sudoku requires combining XV pair logic with standard naked singles and hidden singles. Look for cells where XV constraints reduce candidates to just one or two options, then verify those options against row, column, and box rules. Pay special attention to the negative constraint — pairs of adjacent cells without markers cannot sum to 5 or 10.
How does the negative constraint help in medium XV Sudoku?
When two adjacent cells have no marker, you can eliminate all pairs summing to 5 or 10 from those cells. For example, if a cell could be 1, 2, 3, or 4, and its unmarked neighbor also could be 4, their 1+4 combination is forbidden because it would sum to 5. This removes (1,4) and (4,1) as a valid combination for that pair.
What happens when an X marker is next to a box boundary?
An X marker that crosses a box boundary connects two cells in different boxes. The pair constraint still applies — they must sum to 10 — but they don't share the same box uniqueness rule. This cross-box constraint can force a specific digit into a cell from outside its own box, which is a powerful deduction unavailable in regular Sudoku.
Can a digit appear in both an X pair and a V pair in XV Sudoku?
Yes, if the digit is used in non-overlapping pairs. For example, the digit 1 can be in a V pair (1+4=5) in one location and used without an X or V constraint elsewhere. What matters is that within any single pair of adjacent marked cells, exactly one valid combination applies.
How long does a medium XV Sudoku take?
Most players complete a medium XV Sudoku in 15 to 25 minutes. The V markers resolve quickly due to their tight range. Getting stuck usually means the negative constraint (no marker = no X or V sum) has not been applied to some set of adjacent cells.

More questions? See the full XV Sudoku guide.