The case notes
How a double arrow works
The digits between the circled ends add to the sum of the two end digits. Watch a worked example, then try the idea in a puzzle.
Put it into practice
End circles = middle sum
A double arrow has a circle at each end. Add the two end digits to find the total for the cells between them.
1 + 4 = 5
The circles hold one and four. Together they make five. That is the sum the inner cells must reach.
5 − 2 = 3
One inner cell is two. Five minus two leaves three for the other. The end digits do not count inside the line sum a second time.
1 + 4 = 2 + 3
One plus four at the ends equals two plus three in the middle. Keep those two sides of the double arrow balanced.
Read the transcript
A double arrow has a circle at each end. Add the two end digits to find the total for the cells between them. The circles hold one and four. Together they make five. That is the sum the inner cells must reach. One inner cell is two. Five minus two leaves three for the other. The end digits do not count inside the line sum a second time. One plus four at the ends equals two plus three in the middle. Keep those two sides of the double arrow balanced.
