Platon Sudoku · Sudoku Study

Naked Pair · Step-by-step example

Two cells in the same row, column, or box each contain only the same two candidates. Remove both digits from the other cells in every region shared by the pair.

This course is adapted from Platon Sudoku App. Read the complete example here, then continue learning and practising in the app.

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Recognize the pattern

Two cells in the same row, column, or box each contain only the same two candidates.

How to find it

With candidates visible, find a two-candidate cell and check the rest of its row, column, and box for an identical partner.

What it allows

Remove both digits from the other cells in every region shared by the pair.

Avoid the mix-up

Two cells merely containing the same two digits are not enough if either has a third candidate. A hidden pair is identified by where two digits can go, not by two cells having only those digits.

Step-by-step example · Row

This example starts from a saved intermediate position. Its candidates include earlier logical eliminations; they are not fresh automatic notes.

Blue: evidence. Green: conclusion. Crossed-out digits: eliminated candidates. R1C1 means row 1, column 1.

Step 1 · Observe the pair

These two cells contain only 1 and 3.

These two cells contain only 1 and 3.

Step 2 · Understand the reservation

Digits cannot repeat in row 2. One cell must be 1, the other 3.

Digits cannot repeat in row 2. One cell must be 1, the other 3.

Step 3 · Remove candidates

Remove the marked 1, 3 candidates from other cells in row 2.

Remove the marked 1, 3 candidates from other cells in row 2. R2C2=1, R2C3=1, R2C3=3

What it allows

Remove the marked 1, 3 candidates from other cells in row 2.

Naked Pair · Remove both digits from the other cells in every region shared by the pair.

Step-by-step example · Column

This example starts from a saved intermediate position. Its candidates include earlier logical eliminations; they are not fresh automatic notes.

Blue: evidence. Green: conclusion. Crossed-out digits: eliminated candidates. R1C1 means row 1, column 1.

Step 1 · Observe the pair

These two cells contain only 3 and 9.

These two cells contain only 3 and 9.

Step 2 · Understand the reservation

Digits cannot repeat in column 3. One cell must be 3, the other 9.

Digits cannot repeat in column 3. One cell must be 3, the other 9.

Step 3 · Remove candidates

Remove the marked 3 candidates from other cells in column 3.

Remove the marked 3 candidates from other cells in column 3. R9C3=3

What it allows

Remove the marked 3 candidates from other cells in column 3.

Naked Pair · Remove both digits from the other cells in every region shared by the pair.

Step-by-step example · Box

This example starts from a saved intermediate position. Its candidates include earlier logical eliminations; they are not fresh automatic notes.

Blue: evidence. Green: conclusion. Crossed-out digits: eliminated candidates. R1C1 means row 1, column 1.

Step 1 · Observe the pair

These two cells contain only 3 and 8.

These two cells contain only 3 and 8.

Step 2 · Understand the reservation

Digits cannot repeat in box 5. One cell must be 3, the other 8.

Digits cannot repeat in box 5. One cell must be 3, the other 8.

Step 3 · Remove candidates

Remove the marked 3, 8 candidates from other cells in box 5.

Remove the marked 3, 8 candidates from other cells in box 5. R6C4=3, R6C4=8

What it allows

Remove the marked 3, 8 candidates from other cells in box 5.

Naked Pair · Remove both digits from the other cells in every region shared by the pair.

Practice

This course is adapted from Platon Sudoku App. Read the complete example here, then continue learning and practising in the app.

View on Google Play