The case notes
How a parity line alternates
Adjacent digits on a parity line alternate between odd and even. Watch a worked example, then try the idea in a puzzle.
Put it into practice
Odd and even alternate
A parity line alternates odd and even as you follow it. The digits themselves do not need to rise or fall.
Even · odd · even · odd · even
Here it goes four, five, six, seven. Even, odd, even, odd. So the last cell on the line must be even.
The row removes 2, 4 and 6
The even digits are two, four, six and eight. Four and six are already in this row; so is two, farther along.
The last line cell is 8
That leaves eight. The line tells us to look only at evens, and the ordinary row rule chooses which even one.
Read the transcript
A parity line alternates odd and even as you follow it. The digits themselves do not need to rise or fall. Here it goes four, five, six, seven. Even, odd, even, odd. So the last cell on the line must be even. The even digits are two, four, six and eight. Four and six are already in this row; so is two, farther along. That leaves eight. The line tells us to look only at evens, and the ordinary row rule chooses which even one.
