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Platon Sudoku · Sudoku Study

Locked Triple · Step-by-step example

Three cells in a row–box or column–box intersection contain only three digits between them. Remove those three digits from every other cell in the shared line and box.

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

Recognize the pattern

Three cells in a row–box or column–box intersection contain only three digits between them.

How to find it

Check the three cells where a row or column crosses a box. Look for a combined set of exactly three candidates.

What it allows

Remove those three digits from every other cell in the shared line and box.

Avoid the mix-up

The three cells need not have identical candidates. Every candidate in them must belong to the same three-digit set.

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 triple

These three cells can only use 1, 7, 8. Each digit must occupy one cell.

These three cells can only use 1, 7, 8. Each digit must occupy one cell.
These three cells can only use 1, 7, 8. Each digit must occupy one cell.
Step 2 · See the shared regions

These three cells lie in both row 5 and box 5, so all three digits are reserved in both regions.

These three cells lie in both row 5 and box 5, so all three digits are reserved in both regions.
These three cells lie in both row 5 and box 5, so all three digits are reserved in both regions.
Step 3 · Remove candidates

Remove the marked 7 candidates from the other cells in row 5 and box 5.

Remove the marked 7 candidates from the other cells in row 5 and box 5. R4C6=7, R5C1=7, R5C7=7, R5C8=7, R6C5=7, R6C6=7
Remove the marked 7 candidates from the other cells in row 5 and box 5. R4C6=7, R5C1=7, R5C7=7, R5C8=7, R6C5=7, R6C6=7

What it allows

Remove the marked 7 candidates from the other cells in row 5 and box 5.

Locked Triple · Remove those three digits from every other cell in the shared line and box.
Locked Triple · Remove those three digits from every other cell in the shared line and box.

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 triple

These three cells can only use 1, 4, 7. Each digit must occupy one cell.

These three cells can only use 1, 4, 7. Each digit must occupy one cell.
These three cells can only use 1, 4, 7. Each digit must occupy one cell.
Step 2 · See the shared regions

These three cells lie in both column 8 and box 6, so all three digits are reserved in both regions.

These three cells lie in both column 8 and box 6, so all three digits are reserved in both regions.
These three cells lie in both column 8 and box 6, so all three digits are reserved in both regions.
Step 3 · Remove candidates

Remove the marked 1, 4 candidates from the other cells in column 8 and box 6.

Remove the marked 1, 4 candidates from the other cells in column 8 and box 6. R5C7=4, R5C9=1, R9C8=1, R9C8=4
Remove the marked 1, 4 candidates from the other cells in column 8 and box 6. R5C7=4, R5C9=1, R9C8=1, R9C8=4

What it allows

Remove the marked 1, 4 candidates from the other cells in column 8 and box 6.

Locked Triple · Remove those three digits from every other cell in the shared line and box.
Locked Triple · Remove those three digits from every other cell in the shared line and box.

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