Naked pair practice sheets

Why a "medium" sheet is not the same thing

Most printable sudoku decides difficulty by counting clues. That number is easy to print and a poor guide: a 30-clue board can fall apart to singles while a 34-clue board needs an X-Wing. If you want to practise one specific move, a difficulty label tells you nothing about whether that move will appear.

These sheets are the other way round. Every puzzle is generated, then replayed the way a person solves it — cheapest technique first, one step at a time — and kept only if a naked pair shows up on that path. The filter runs in your browser each time the page loads, so the set is new every visit.

What you are looking for

A naked pair is two cells in the same unit that hold exactly the same two candidates and nothing else. Two cells, two digits, so those two digits must sit in those two cells in some order — and cannot appear anywhere else in the row, column or box they share.

Two things make it easy to miss:

• The pair has to be the whole candidate list. Two cells showing 4, 7 plus a third digit are not a pair. That is why the sheet has a candidate marks option: without pencil marks you are asked to hold nine lists in your head at once.
• It works along one unit at a time. A pair seen in a row removes digits from that row only. The same two cells may also be a pair in their box, in which case it removes from both — check the other unit before moving on.

What the grader guarantees

Every puzzle on the sheet needs at least one naked pair, and nothing on it asks for more than one tier above that. In practice that means: singles and pairs first, and the hardest extra step you can meet is an X-Wing. The filter never relaxes to fill a sheet, so if one ever comes up short, press New set — that is the filter refusing to hand you the wrong kind of puzzle.

That guarantee is worth more than a difficulty word. It means the sheet is about one skill from the first cell to the last, instead of six puzzles where one happens to contain the pattern you wanted.

Printing it

Set scale to 100% (some browsers call it "Actual size"). With four puzzles per page the boards are 78 mm, which is a classroom handout; two per page leaves room for pencil marks between them; one per page fills most of the sheet.

Turn on Candidate marks if you are still learning to spot pairs. The printed marks are the same 3×3 layout the game uses on screen, so the habit transfers. Turn on Answer page if you want the solutions on separate sheets at the end, numbered to match.

If a puzzle refuses to open

Naked pairs hide best in boxes with many empty cells, so scan boxes before rows. If you have marked a pair and nothing much falls out, the pair was real but not useful yet — that happens, and it is not a mistake. The full guide to naked pairs works through a position where the elimination is the whole point, and sorts the related moves (hidden pair, naked triple) so you know which one you are looking at.

When pairs come easily, the pointing pairs sheet is the next thing that stops people on medium puzzles.