Lesson 4 · Solving routine
Scanning
Search for one number at a time instead of jumping randomly around the board.
See the logic move
Use Next to reveal each reason. On the final step, tap the highlighted cell to complete the move yourself.
Step 1 of 3
Choose 5
We will scan only for number 5.
Select an empty cell to see its legal candidates and why the other digits are blocked.
- 1
Pattern: These cells form the logical pattern that proves the move. R1C1, R2C6, R8C9.
What the board is showing
Explain it simply
Pick a number and sweep through the boxes. Rows and columns show where it cannot go.
Step by step
- Choose a number.
- Find boxes missing that number.
- Use rows and columns to block cells.
- Place it when only one cell remains.
From demonstration to independent solving
Prove the move yourself
What you should be able to do
Scan one digit systematically across boxes and use crossing rows and columns to find its only legal home.
Read the exact board evidence
In the top-right box, the placed 5s at R1C1 and R2C6 block the first two rows. A 5 at R8C9 also blocks column 9. Seven cells are therefore unavailable for 5, and the remaining square R3C7 is forced.
When the logic is strong enough
A box scan is complete only after every alternative square has a visible row, column or box reason that rules it out.
Train the pattern without guessing
Choose digit 5 and visit all nine boxes in order. Mark only boxes where 5 is missing, then look for one with two crossing lines that leave a single square.
Quick check: What should you do after a successful scan places a number?
Scan again because the new number may unlock another placement.
Turn logic into skill