Permalink Submitted by Mike on Mon, 07/27/2026 - 17:24.
The first steps are: R1C3=2, R5C5=7, R1C7=4, R4C5=R1C6=5, R8C7=R4C9=R6C1=8, R4C3=R6C7=R2C9=R8C1=6, R8C3=9 (naked single).
Now let's look at the digits 6, 8 and 9 in Box 8. Their possible positions are all at most R7C4, R7C5 and R7C6, so these three cells must contain these three digits. Therefore, other digits cannot be in these cells. It follows that R9C4=2 and R9C5=4.
Hidden Triplet
The first steps are: R1C3=2, R5C5=7, R1C7=4, R4C5=R1C6=5, R8C7=R4C9=R6C1=8, R4C3=R6C7=R2C9=R8C1=6, R8C3=9 (naked single).
Now let's look at the digits 6, 8 and 9 in Box 8. Their possible positions are all at most R7C4, R7C5 and R7C6, so these three cells must contain these three digits. Therefore, other digits cannot be in these cells. It follows that R9C4=2 and R9C5=4.