We only need to measure the length between the two endpoints to know the length of the line segment.
The length of the line segment has nothing to do with the two arrows on the side, and this arrow is only the interference of solving the problem.
The rules for line segments are as follows:
2 points: 1.
3 points: 2+ 1=3.
4 points: 3+2+ 1=6.
5 points: 4+3+2+ 1= 10.
N point: (n-1)+... 3+2+1= n (n-1)/2.
This rule is for reference only, don't memorize it. Generally speaking, the second-level exam will not exceed 6 points. Therefore, parents can try to draw different points and let their children draw line segments and count them.