The case notes
When every X and V 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
X: 10 · V: 5
You already know the letters: an X marks a pair summing to ten, and a V marks a pair summing to five.
No mark means neither sum
This puzzle says all Xs and Vs are shown. That makes a bare edge a clue too: its two digits cannot add to ten or five.
4 + 6 needs an X
There is a four here. Six next door would make ten, but there is no X. Six is out.
4 + 1 needs a V
One next door would make five, but there is no V either. One is out too. The missing marks tell us what cannot go here.
Read the transcript
You already know the letters: an X marks a pair summing to ten, and a V marks a pair summing to five. This puzzle says all Xs and Vs are shown. That makes a bare edge a clue too: its two digits cannot add to ten or five. There is a four here. Six next door would make ten, but there is no X. Six is out. One next door would make five, but there is no V either. One is out too. The missing marks tell us what cannot go here.
