Nine squares add up to fifteen, and there are the following situations, as shown in the figure:

Jiugongge has one and only one basic solution and eight forms. The sum of 1-9 is 45,45 ÷ 3 = 15, so the magic sum of nine squares =15.

Extended data:

On the river map, black spots and white spots arranged in several arrays contain infinite mysteries; The pattern on Luoshu just corresponds to nine numbers from 1 to 9, and the sum of three numbers on vertical, horizontal, oblique and three lines is equal to 15. At that time, people didn't know it was the third-order magic square in modern mathematics. They called this mysterious arrangement of numbers Nine palace map.

Scholars at home and abroad have conducted long-term exploration and research on this issue, believing that it is the crystallization of the spiritual thinking of Chinese ancestors and the first milestone of ancient civilization in China. The Book of Changes and Hong Fan play an extremely important role in the history of China's cultural development, and have far-reaching influences on philosophy, politics, military science, ethics, aesthetics and literature. As the source of China's history and culture, Hetuluo's works have contributed a lot.