The case notes
Use a pair of cells to remove candidates
A naked pair is two cells that can hold the same two digits and no others. The pair can remove those digits elsewhere in its row, column or box. Watch a worked example, then try the idea in a puzzle.
Put it into practice
Two cells reserve two digits
A naked pair is two cells that can hold the same two digits and no others. The pair can remove those digits elsewhere in its row, column or box.
Row needs 1, 2, 3
The top row needs one, two and three. For each of its first three cells, start with those three possibilities.
First two cells: {1, 2}
Three already appears lower down in column one, and again in column two. So the first two cells cannot be three. They are both restricted to one or two.
1 and 2 are reserved
Those two cells must take one and two, in either order. Both digits are reserved. The third cell in their row cannot use either.
r1c3 = 3
That leaves three in the third cell. A pair can settle another cell before we know which member is one and which is two.
Read the transcript
A naked pair is two cells that can hold the same two digits and no others. The pair can remove those digits elsewhere in its row, column or box. The top row needs one, two and three. For each of its first three cells, start with those three possibilities. Three already appears lower down in column one, and again in column two. So the first two cells cannot be three. They are both restricted to one or two. Those two cells must take one and two, in either order. Both digits are reserved. The third cell in their row cannot use either. That leaves three in the third cell. A pair can settle another cell before we know which member is one and which is two.
