Let's Make Number Place (Elementary course)
Let's Make Number Place : Step 7
11. Consider the constraints of the rows.
Let's see where a 6 goes in the row shown in dotted line. We have to put a 6 to either H or I.
Whichever is fine, but say we set I 6. We need to proceed carefully from now on, or it may break down.
12. Use 9s.
So far, the untouched numbers are 2s, 8s, and 9s. Now, let's use 9s. Place a 9 here.
Then, the marked cell becomes 9.
Let's place a 9 on the exposed cell in the bottom center block. Then, in the column shown in the dotted line, only the marked cell can accept a 9.
We need to go on very carefully or the puzzle may break down quite easily. And it's time for giving up our policy not to put numbers on the exposed cells.
