The case notes
When every X is shown
All markers named in this lesson are shown. Watch a worked example, then try the idea in a puzzle.
Put it into practice
All Xs are shown
An X between two cells means they add to ten. This puzzle tells us every possible X has been marked.
No X means no sum of 10
Now look at this four and its neighbour. There is no X between them. That absence is a clue: the neighbour cannot make ten with four.
4 + 6 needs an X
Four plus six is ten. So six cannot go here. We cross out six, even though the target cell is still unsolved.
Read which marks are complete
Only Xs are guaranteed here. A missing V would say nothing unless the puzzle also tells us that every V is shown.
Read the transcript
An X between two cells means they add to ten. This puzzle tells us every possible X has been marked. Now look at this four and its neighbour. There is no X between them. That absence is a clue: the neighbour cannot make ten with four. Four plus six is ten. So six cannot go here. We cross out six, even though the target cell is still unsolved. Only Xs are guaranteed here. A missing V would say nothing unless the puzzle also tells us that every V is shown.
