LOCKED CELLS #3

(if this is your first visit scroll down to the first post, june 12, to begin the lecture)

And so, the next step will be totally deductionary. We will look into grid # 5 (center).

In it you will see two options marked for the value 9 (upper left and.. upper right).

Since the upper left option lies within the column where the values 8-9 are already taken.

You may scratch off the upper left option and write the value 9 on the upper right cell.

Not only vertical columns may be "locked in" but also horizontal rows as well..