The case notes
How an X-sum clue works
The first digit from the clue gives X. The first X digits, including that digit, add up to the outside clue. Watch a worked example, then try the idea in a puzzle.
Put it into practice
First digit = number of cells
An X-sum clue sits outside a row or column. Begin at the clue and read the first digit. That digit tells you how many cells to count.
3 means count 3 cells
Here the first digit is three. So count the first three cells, including that three itself. Stop there; the rest of the row is outside this sum.
3 + 1 + 2 = 6
The outside clue is six. Three and one are already in those first three cells. That leaves two for the third cell.
Length first. Sum second.
The first digit sets the length. The clue gives the total. Always count from the side where the clue sits.
Read the transcript
An X-sum clue sits outside a row or column. Begin at the clue and read the first digit. That digit tells you how many cells to count. Here the first digit is three. So count the first three cells, including that three itself. Stop there; the rest of the row is outside this sum. The outside clue is six. Three and one are already in those first three cells. That leaves two for the third cell. The first digit sets the length. The clue gives the total. Always count from the side where the clue sits.
