Sudoku Techniques Quiz: Hidden Singles, Pairs and X-Wings
This Sudoku techniques quiz shows the logical steps solvers use when easy moves run out. Play 10 interactive questions on pencil marks, naked singles, hidden singles, naked pairs, pointing pairs, X-Wings, Swordfish, the rules of the grid, the 17-clue minimum and the puzzle's American and Japanese roots.
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🎯 Daily Trivia Challenge • 🧠 10 Questions • ⏱️ 150 Seconds
Rules
In standard Sudoku, each row, column and box must contain what?
Marks
What are pencil marks?
Naked
What is a naked single?
Hidden
What is a hidden single?
Pair
Two cells in a row share only the candidates 4 and 7. What can you do?
Pointing
What is a pointing pair?
X-Wing
An X-Wing uses a candidate limited to two cells in each of how many rows?
Swordfish
How does a Swordfish differ from an X-Wing?
Clues
What is the fewest clues a standard Sudoku can have and still have one solution?
Origin
Under which name did Sudoku first appear in an American magazine?
Your score
0/10
Scroll down to see the explanation for each question.
Explanations: answer key for all 10 questions
- Q1: In standard Sudoku, each row, column and box must contain what?
Answer: The digits 1 to 9 once each
The grid is 9 by 9.
- Q2: What are pencil marks?
Answer: Small notes of possible digits
They are also called candidates.
- Q3: What is a naked single?
Answer: A cell with only one possible digit
It can be filled at once.
- Q4: What is a hidden single?
Answer: A digit that fits only one cell in a row, column or box
Other candidates in that cell can be ignored.
- Q5: Two cells in a row share only the candidates 4 and 7. What can you do?
Answer: Remove 4 and 7 from other cells in that row
This is a naked pair.
- Q6: What is a pointing pair?
Answer: A candidate in a box limited to one row or column
It removes that digit along the line.
- Q7: An X-Wing uses a candidate limited to two cells in each of how many rows?
Answer: Two
The cells share the same two columns.
- Q8: How does a Swordfish differ from an X-Wing?
Answer: It uses three rows and columns
It is a bigger version.
- Q9: What is the fewest clues a standard Sudoku can have and still have one solution?
Answer: 17
This was proved in 2012.
- Q10: Under which name did Sudoku first appear in an American magazine?
Answer: Number Place
Japan's Nikoli later named it Sudoku.
Sudoku Techniques Quiz – Hidden Singles, Pairs and X-Wings
Sudoku asks you to fill a 9 by 9 grid so each row, column and 3 by 3 box contains the digits 1 to 9. Many solvers write small pencil marks to track which digits are still possible in each cell.
The simplest moves are naked singles, where a cell has one candidate, and hidden singles, where a digit fits only one place in a unit. Naked pairs and pointing pairs then remove candidates from nearby cells.
Harder puzzles need patterns such as the X-Wing and Swordfish. The puzzle first appeared as Number Place in an American magazine in 1979, and the Japanese publisher Nikoli gave it the name Sudoku.
What This Quiz Teaches
Puzzle fans will enjoy these questions.
- What the rules are
- How pencil marks help
- What singles and pairs are
- How X-Wings work
- Where Sudoku began
Did You Know?
- Howard Garns is credited with creating Number Place.
- Sudoku became a global craze around 2005.
- A good puzzle needs only logic, not guessing.
- Variants add diagonal or killer rules.
- The name shortens a Japanese phrase about single digits.
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