The case notes
How an arrow adds up
The digits on an arrow sum to the digit in its circle. Watch a worked example, then try the idea in a puzzle.
Put it into practice
Circle = shaft total
Here is a Sudoku arrow. The circle at its base holds the total; every cell along the shaft contributes to that number.
9 − 5 = 4
The circle is nine. Five is already on the shaft, so the other two cells must add to four.
No 2 + 2 in one row
Two and two would make four, but these cells share a Sudoku row. They cannot repeat. The pair must be one and three.
The column chooses 3
There is already a one higher up this column. So this shaft cell cannot be one. It takes three.
5 + 3 + 1 = 9
The last cell is one. Five, three and one make nine. The arrow gave us a sum; Sudoku fixed the order.
Read the transcript
Here is a Sudoku arrow. The circle at its base holds the total; every cell along the shaft contributes to that number. The circle is nine. Five is already on the shaft, so the other two cells must add to four. Two and two would make four, but these cells share a Sudoku row. They cannot repeat. The pair must be one and three. There is already a one higher up this column. So this shaft cell cannot be one. It takes three. The last cell is one. Five, three and one make nine. The arrow gave us a sum; Sudoku fixed the order.
