What defines a hidden pair?

Two digits that can only go in the same two cells of a unit

What can you remove after finding a hidden pair?

All other candidates from those two cells

What is a naked pair?

Two cells with only the same two candidates

Sudoku Hidden Pair Quiz: Candidates, Units and Eliminations

This sudoku hidden pair quiz pencils in candidates and finds a secret partnership. Play 10 interactive questions on rows, columns and boxes, candidates, what makes a pair hidden, how it eliminates other candidates in those two cells, the difference from a naked pair, hidden triples, Howard Garns's Number Place of 1979, the name given by Nikoli and the 17-clue minimum.

Start Sudoku Hidden Pair Quiz

🎯 Daily Trivia Challenge • 🧠 10 Questions • ⏱️ 150 Seconds

Question 1 / 10 Time: 150s

Units
Which three units must each contain 1 to 9 once?
Cand
What are candidates?
Hidden
What defines a hidden pair?
Remove
What can you remove after finding a hidden pair?
Naked
What is a naked pair?
Diff
Where does a naked pair remove candidates?
Triple
What extends the hidden pair idea?
Garns
Who created the puzzle published as Number Place in 1979?
Name
Which Japanese company gave Sudoku its name?
Clues
What is the minimum number of clues for a unique Sudoku?

Explanations: answer key for all 10 questions

Q1: Which three units must each contain 1 to 9 once?
Answer: Rows, columns and boxes
Each unit has nine cells.
Q2: What are candidates?
Answer: Possible digits for a cell
Often written small.
Q3: What defines a hidden pair?
Answer: Two digits that can only go in the same two cells of a unit
They hide among other candidates.
Q4: What can you remove after finding a hidden pair?
Answer: All other candidates from those two cells
The cells must hold the pair.
Q5: What is a naked pair?
Answer: Two cells with only the same two candidates
Eliminates from the rest of the unit.
Q6: Where does a naked pair remove candidates?
Answer: From other cells in the unit
Unlike a hidden pair.
Q7: What extends the hidden pair idea?
Answer: Hidden triples
Three digits in three cells.
Q8: Who created the puzzle published as Number Place in 1979?
Answer: Howard Garns
Dell Magazines published it.
Q9: Which Japanese company gave Sudoku its name?
Answer: Nikoli
It means single digits, roughly.
Q10: What is the minimum number of clues for a unique Sudoku?
Answer: 17
Proved in 2012.

Two Digits, Two Cells

In Sudoku, each row, column and 3 by 3 box must contain the digits 1 to 9 exactly once. Solvers write candidates, possible digits for each cell, and use techniques to remove them until each cell has one answer.

A hidden pair appears when two digits can only go in the same two cells of a unit. Those two cells must hold that pair, so all other candidates in them can be removed. A naked pair is different: two cells contain only the same two candidates, so those digits can be removed from other cells in the unit. Hidden triples extend the idea to three digits in three cells.

Howard Garns created the puzzle, published by Dell Magazines as Number Place in 1979. The Japanese company Nikoli gave it the name Sudoku, roughly meaning single digits. In 2012 researchers proved that a unique Sudoku needs at least 17 clues.

What This Quiz Teaches

Puzzle fans will enjoy these questions.

How Sudoku units work
What candidates are
How hidden pairs work
How naked pairs differ
Where Sudoku came from

Did You Know?

Pencil marks keep track of candidates.
X-Wing is an advanced technique.
Newspapers spread Sudoku in 2005.
Killer Sudoku adds sums.
Good puzzles need no guessing.