The case notes
Find the only place for a digit
A hidden single asks where a digit can go in a row, column or box. We need a one somewhere in this top row. Watch a worked example, then try the idea in a puzzle.
Put it into practice
Where can 1 go?
A hidden single asks where a digit can go in a row, column or box. We need a one somewhere in this top row.
Three gaps · 1, 2, 5 missing
The row is missing one, two and five. It has three empty cells, so we cannot fill a gap just by reading the row.
Column 2 blocks 1
One already appears in the second column. So it cannot go in the second gap of our row.
Column 5 blocks 1
There is also a one in the fifth column. That blocks the other gap. Only the first cell is left for one.
Only place for 1: r1c1
Place one in the first cell. That cell still had other possible digits, but it was the only place for one in its row.
Read the transcript
A hidden single asks where a digit can go in a row, column or box. We need a one somewhere in this top row. The row is missing one, two and five. It has three empty cells, so we cannot fill a gap just by reading the row. One already appears in the second column. So it cannot go in the second gap of our row. There is also a one in the fifth column. That blocks the other gap. Only the first cell is left for one. Place one in the first cell. That cell still had other possible digits, but it was the only place for one in its row.
