Naked Pairs: Eliminating Candidates Together

Naked Pairs is your first step into intermediate Sudoku techniques. This powerful method uses pairs of cells to eliminate candidates across a row, column, or box.

What is a Naked Pair?

A naked pair occurs when two cells in the same row, column, or box both contain exactly the same two candidates. When this happens, you know these two numbers must occupy these two cells - you just don't know which goes where yet.

The Key Insight

If two cells in a region can only contain (4, 7), then:

• One cell will have 4, the other will have 7
• No other cell in that region can contain 4 or 7
• You can eliminate 4 and 7 from all other cells in that region

How to Find Naked Pairs

Look for two cells in the same row, column, or box that:

1. Each have exactly two candidates
2. Have the exact same two candidates

Example

Imagine a row where:

• Cell A has candidates (2, 5)
• Cell B has candidates (2, 5)
• Cell C has candidates (2, 5, 8)
• Cell D has candidates (5, 8, 9)

Cells A and B form a naked pair! You can now:

• Remove 2 and 5 from cell C (leaving just 8)
• Remove 5 from cell D (leaving (8, 9))

Why It Works

The logic is simple but powerful: since cells A and B can only be 2 and 5, one of them must be 2 and the other must be 5. Therefore, no other cell in that row can use those numbers.

Common Mistakes

• Requiring both numbers everywhere: The pair just needs the same two candidates - they don't both need to appear in every other cell
• Missing non-obvious pairs: Sometimes pairs are in boxes, not just rows or columns
• Forgetting to eliminate: Finding the pair is just step one - you must eliminate from other cells
• Confusing with triples: A pair is exactly two candidates in exactly two cells

Scanning Strategy

1. Look at each row, column, and box
2. Find cells with exactly 2 candidates
3. Check if any two cells have matching candidates
4. Eliminate those candidates from all other cells in that region

Impact on Solving

Naked pairs often create a cascade effect:

• Eliminating candidates reveals naked singles
• Those placements create new pairs
• The puzzle starts to unlock

Related Techniques

• Hidden Pairs: The opposite approach - pairs that hide among other candidates
• Naked Triples: The same concept but with three cells and three candidates
• Pointing Pairs: A different use of pairs that we'll cover next

Practice Tips

1. Start by looking for cells with only 2 candidates
2. Mark them visually to spot matches easier
3. Remember to check all three regions (row, column, box)
4. After finding a pair, carefully eliminate from all affected cells

Next Steps

Once you're comfortable with naked pairs, try:

• Hidden Pairs - Finding pairs that aren't immediately obvious
• Pointing Pairs - Using box-row/box-column intersections
• Naked Triples - Extending this technique to three cells