Introduction

The Obvious Triples technique is a natural extension of Obvious Pairs and an essential intermediate Sudoku solving method. While Obvious Pairs involves two cells sharing two candidates, Obvious Triples involves three cells sharing three candidates among them, creating even more powerful elimination opportunities.

Understanding Obvious Triples helps you solve medium to hard puzzles more efficiently. This technique works by recognizing when three cells in a 3×3 block contain only three candidates total (distributed among them), which means those three numbers must go in those three cells, allowing you to eliminate them from other cells in the block.

What Is the Obvious Triples Technique?

The Obvious Triples technique is a Sudoku solving method built upon Obvious Pairs. Instead of two cells sharing two candidates, Obvious Triples involves three cells that together contain exactly three candidates. These three cells share these three numbers among them, meaning one of each number must go in one of these cells.

Since these three numbers must occupy these three cells, they cannot appear in any other cells within that 3×3 block. This allows you to remove these candidates from all other cells' notes in the block, which often reveals new Obvious Singles or creates other solving opportunities.

Obvious Triples is also known as Naked Triples, and it's an intermediate technique that becomes essential when progressing from medium to hard puzzles. It requires proper notes placement to identify, as you need to see all candidates in cells to recognize the pattern.

Key Points

Understanding these fundamentals helps you master Obvious Triples:

Extension of Obvious Pairs: Obvious Triples works the same way as Obvious Pairs but with three cells and three candidates
Requires notes: Obvious Triples can only be identified when you have proper notes showing all possible candidates
Three cells, three candidates: The technique applies when three cells in a block together contain exactly three candidates (distributed among them)
Elimination opportunity: The triple's candidates can be removed from all other cells in the same 3×3 block
Works in blocks: While triples can occur in rows and columns, this technique focuses on 3×3 blocks
Creates chain reactions: After elimination, new Obvious Singles often appear, leading to more placements

How It Works (Step-by-Step)

Follow these steps to identify and apply the Obvious Triples technique:

Step 1: Enable Notes or Pencil Marks

Start by enabling notes mode on your Sudoku grid. Fill in all possible candidates for each empty cell based on what numbers are already present in that cell's row, column, and box. Obvious Triples cannot be identified without visible notes showing all candidates.

Step 2: Scan Each 3×3 Block Systematically

Work through each of the nine 3×3 blocks one at a time. Look for cells that have two or three candidates in their notes. These are potential members of an Obvious Triple.

Step 3: Look for Three Cells Sharing Three Candidates

Within each block, check if any three cells together contain exactly three candidates. For example, one cell might have candidates 1 and 5, another has 1 and 8, and a third has 5 and 8. Together, these three cells contain exactly three candidates: 1, 5, and 8.

Step 4: Verify the Triple

Confirm that the three cells are in the same 3×3 block and that together they contain exactly three candidates—no more, no less. The candidates can be distributed in any combination among the three cells (like 1,5; 1,8; 5,8 or 1,5,8; 1,5; 5,8, etc.).

Step 5: Eliminate Candidates from Other Cells

Since the three numbers in the triple must go in these three cells, remove those candidates from all other cells' notes within the same 3×3 block. This elimination is the key benefit of identifying Obvious Triples.

Step 6: Update Your Notes

After eliminating candidates, update your notes throughout the block. Removing candidates may reveal new Obvious Singles—cells that now have only one candidate remaining.

Step 7: Apply Obvious Singles

After eliminating candidates from the Obvious Triple, scan the block for cells with only one candidate remaining. These are Obvious Singles that you can place immediately. Continue this process as each placement may create new opportunities.

Examples

Here are practical examples demonstrating how Obvious Triples works:

Example 1: Basic Obvious Triple Pattern

You're examining the top left 3×3 block. Its three bottom cells contain notes: one cell has 1 and 5, another has 1 and 8, and the third has 5 and 8. Together, these three cells contain exactly three candidates: 1, 5, and 8.

This means that numbers 1, 5, and 8 must go in these three cells (though you don't know which number goes in which cell yet). Since these three numbers must occupy these three cells, they cannot appear in any other cells within this block. You remove 1, 5, and 8 from all other cells' notes in the block.

Example 2: Different Candidate Distribution

In another block, you find three cells with different candidate distributions: one cell has 2, 3, and 7; another has 2 and 3; and a third has 3 and 7. Together, these three cells contain exactly three candidates: 2, 3, and 7. This is still an Obvious Triple, even though the candidates are distributed differently among the cells.

You eliminate 2, 3, and 7 from all other cells in the block. After this elimination, you notice that one cell now has only candidate 4 remaining, and another has only candidate 9. These are Obvious Singles, so you place 4 and 9 in their respective cells.

Example 3: Triple Revealing Multiple Singles

In a different block, you identify an Obvious Triple of 4, 6, and 9. You eliminate these candidates from other cells in the block. This elimination reveals that three other cells now have only one candidate each: one has only 1, another has only 3, and a third has only 8. You place all three numbers, making significant progress in the puzzle.

Example 4: Not an Obvious Triple

You're looking at a block where three cells have candidates, but together they contain four different numbers: one cell has 1 and 2, another has 2 and 3, and a third has 3 and 4. Together, these cells contain 1, 2, 3, and 4—four candidates, not three. This is not an Obvious Triple, so the technique doesn't apply.

Example 5: Chain Reaction After Elimination

You identify an Obvious Triple of 1, 5, and 8 in a block and eliminate these candidates from other cells. One cell that previously had candidates 2, 3, 5, 8, 9 now has only 2, 3, and 9. This doesn't create an immediate single, but it reduces the cell's possibilities. Later, after other eliminations, this cell becomes a single candidate, demonstrating how Obvious Triples set up future placements.

How Obvious Triples Relates to Other Techniques

Obvious Triples is part of a family of related techniques:

Obvious Pairs

Obvious Triples is built upon Obvious Pairs, where two cells share exactly two candidates. The logic is identical—if cells share candidates, those candidates can be eliminated from other cells in the unit. Obvious Triples extends this concept to three cells and three candidates.

Obvious Singles

Obvious Singles occur when a cell has only one candidate remaining. Obvious Triples often creates Obvious Singles after eliminating candidates. Both techniques rely on proper notes placement and work together to solve puzzles systematically.

Hidden Triples

Hidden Triples is the opposite pattern, where three candidates appear in only three cells of a unit, but those cells may have other candidates as well. Understanding both Obvious and Hidden Triples gives you multiple ways to identify elimination opportunities.

When to Use Obvious Triples

Obvious Triples is most effective when:

Notes are complete: You've filled in notes for all empty cells in the block
Obvious Pairs are exhausted: After checking for pairs, look for triples
Medium to hard puzzles: This technique becomes essential when progressing from medium to hard difficulty
Multiple candidates visible: When cells have 2-4 candidates, Obvious Triples become more likely to appear

Common Mistakes to Avoid

Avoid these errors when using Obvious Triples:

Not checking candidate totals: The three cells must together contain exactly three candidates—if they contain four or more, it's not an Obvious Triple
Mixing units: The three cells must be in the same 3×3 block (or row/column if applying the technique there)
Forgetting to eliminate: After identifying a triple, always remove those candidates from other cells in the unit
Not updating notes: After elimination, update your notes to see new opportunities
Overlooking resulting singles: After elimination, always check for new Obvious Singles that may have appeared

Tips for Finding Obvious Triples

These tips help you identify Obvious Triples more efficiently:

Scan systematically: Check each block methodically rather than randomly
Look for cells with 2-3 candidates: These are potential triple members
Count candidate totals: When you find three cells with limited candidates, count how many different candidates they contain together
Work block by block: Complete one block before moving to the next
Update as you go: After each elimination, update notes immediately to see new patterns

Summary

The Obvious Triples technique is a powerful intermediate Sudoku solving method that extends Obvious Pairs to three cells and three candidates. By recognizing when three cells in a 3×3 block together contain exactly three candidates, you can eliminate those candidates from all other cells in the block, often creating Obvious Singles and making significant progress.

This technique requires proper notes placement and works best in medium to hard puzzles where basic techniques and Obvious Pairs are insufficient. Mastering Obvious Triples prepares you for more advanced techniques and is essential for progressing to harder difficulty levels.

Remember that Obvious Triples works together with Obvious Singles—after eliminating candidates from a triple, always scan for new singles that may have appeared. This systematic approach of identifying triples, eliminating candidates, and finding singles creates an effective solving cycle that helps you complete puzzles efficiently.

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❓ FAQ

Q1: What's the difference between Obvious Triples and Naked Triples?

They're the same technique—different names for the same method. Both refer to when three cells in a unit together contain exactly three candidates, allowing elimination of those candidates from other cells in that unit.

Q2: Do Obvious Triples only work in 3×3 blocks?

No. While this guide focuses on blocks, Obvious Triples can occur in rows and columns as well. The same logic applies: if three cells in a row or column together contain exactly three candidates, those candidates can be eliminated from other cells in that row or column.

Q3: What if the three cells together contain more than three candidates?

If the three cells together contain four or more candidates, it's not an Obvious Triple. The technique requires exactly three cells containing exactly three candidates total. If cells contain additional candidates, you may have a Hidden Triple instead, which is a different technique.

Q4: How do I know when to look for Obvious Triples?

Look for Obvious Triples when you've filled in notes for all empty cells and have already checked for Obvious Pairs. In medium to hard puzzles, Obvious Triples become essential for making progress after pairs are exhausted.

Q5: Can Obvious Triples appear in rows or columns too?

Yes. While this guide emphasizes 3×3 blocks, Obvious Triples work in any unit: rows, columns, or blocks. The same principle applies: three cells sharing exactly three candidates allow elimination from other cells in that unit.

Q6: What happens after I eliminate candidates from an Obvious Triple?

After eliminating the triple's candidates from other cells, update your notes. You'll often find that some cells now have only one candidate remaining—these are Obvious Singles that you can place immediately. This chain reaction is one of the technique's main benefits.

Q7: How is Obvious Triples different from Hidden Triples?

Obvious Triples occur when three cells together contain exactly three candidates (and no others in those cells). Hidden Triples occur when three candidates appear in only three cells of a unit, but those cells may have other candidates as well. Both eliminate candidates, but they're identified differently.

Q8: Should I fill in all notes before looking for Obvious Triples?

Yes, for best results. Obvious Triples can only be identified when you can see all candidates in cells. If notes are incomplete, you might miss triples or incorrectly identify them. Complete notes give you the full picture needed to spot this pattern accurately.

Obvious Triples Technique in Sudoku: Complete Guide for Intermediate Players