Question 1: Because there are only 1 nails in the drawing, the nails in the drawing are connected with all the nails in the periphery, so the whole drawing is divided into several small triangles, and the number of small triangles in the interior is equal to the number of nails in the periphery (simply expressed in mathematical language, the number of nails in the periphery can form a non-repetitive line with the nails in the interior, and each pair can form a triangle, because the lines in the interior and the lines formed in the periphery are different. So there is a small triangle), because each nail is 1cm horizontally and vertically, it can be proved that each small triangle is 1/2 square cm, so we can know that the relationship between a and s is s=a/2.

Question 2: The analogy question 1 says that the number of internal triangles is also equal to the number of external nails, and the answer is also s=a/2.

Why are the interesting questions of primary school students more and more like those I used to take part in mathematical models, which makes these friends very painful?