What do X and V mean in XV sudoku?

X marks two cells that sum to 10; V marks two cells that sum to 5, from the Roman numerals X=10 and V=5.

What pairs make a V in XV sudoku?

Pairs summing to 5: {1,4} and {2,3}.

Does XV sudoku have a negative constraint?

Often yes — if the puzzle states all marks are given, an unmarked adjacent pair sums to neither 5 nor 10.

XV Sudoku: Rules & How to Solve

X marks a pair summing to 10, V marks a pair summing to 5. A clean additive variant hiding on the cell borders.

The rule

An X between two cells means they sum to 10; a V means they sum to 5. (XV combines the Roman numerals: X = 10, V = 5.) Many puzzles also use a negative constraint — if no X or V is shown, the pair sums to neither.

How to solve xv sudoku

V pairs are tiny

A V pair sums to 5, so it's one of {1,4} or {2,3} — only two options, which prunes fast.

X pairs from small clues

An X pair sums to 10: {1,9}, {2,8}, {3,7}, or {4,6}, never two 5s since digits can't repeat across the bar.

Mind the negative constraint

When the rules say all X and V are given, two neighbours with no symbol can't sum to 5 or 10 — a quiet but powerful elimination.

Frequently asked questions

What do X and V mean in XV sudoku?: X marks two cells that sum to 10; V marks two cells that sum to 5, from the Roman numerals X=10 and V=5.
What pairs make a V in XV sudoku?: Pairs summing to 5: {1,4} and {2,3}.
Does XV sudoku have a negative constraint?: Often yes — if the puzzle states all marks are given, an unmarked adjacent pair sums to neither 5 nor 10.

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