Hidden Pair in Sudoku: Two Digits, Two Cells
A naked pair shows itself: two cells with the same two notes. A hidden pair is buried under extra candidates, and you find it by asking where each digit can go. Cells are named by row and column: r4c7 is row 4, column 7.
Step 1 of 4
Two digits, the same two cells
Look at column 7. The 4 fits only the ringed cells, r4c7 and r8c7. So does the 8. Those two cells must hold the 4 and the 8, one each, even though their notes show more.
That's a hidden pair: two digits that fit only the same two cells of a row, column or box. Those cells can hold nothing else, so strike their other candidates. r4c7 loses 2 and 6, and r8c7 loses 1.
Use the hidden pair
A hidden pair removes candidates from its own two cells, never from the rest of the column. So check the digits it took away: each one now has fewer places to go in the rows of the pair's cells.
Your move
Clear the other candidates from the pair, then place the digit it unlocks.
What's left in the pair
Once you use the pair, what is left in r4c7?
Find the hidden pair
Every empty cell has its candidates pencilled in, and none has just one. Look for two digits that share the same two cells of a row, column or box.
Your move
Find the hidden pair that unlocks a digit, then place it.
What you learned
- A hidden pair is two digits that fit only the same two cells of a row, column or box.
- Those two cells hold nothing else: strike their other candidates.
- The digits you strike can leave a single somewhere else, as row 4's 2 and row 6's 6 did here.
In this course
Unit 1The rules
Unit 2Solving techniques
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