Mathematical expression:1+2+3+4+...+n = (n+1) n/2.
Example:
1+2+3+...+ 100
=( 1+ 100)× 100/2
= 10 1× 100/2
= 10 100/2
=5050
At the age of seven, Gauss went to school for the first time. Nothing special happened in the first two years. 1787 years old, Gauss 10. He entered the first math class. Children have never heard of such a course as arithmetic before. The math teacher is Buttner, who also played a certain role in the growth of Gauss. A story that is widely circulated all over the world says that when Gauss was at 10, by adding all the integers from 1 to 100, he worked out the arithmetic problem that Butner gave to the students. As soon as Butner described the question, Gauss got the correct answer.
However, this is probably an untrue legend. According to the research of E·T· Bell, a famous mathematical historian who has studied Gauss, Butner gave the children a more difficult addition problem: 81297+81495+81693+…+100899.
Of course, this is also a summation problem of arithmetic progression (the tolerance is 198 and the number of items is 100). As soon as Butner finished writing, Gauss finished the calculation and handed in the small tablet with the answers written on it. E. T. Bell wrote that in his later years, Gauss often liked to talk about this matter with people, saying that only his answer was correct at that time, and all the other children were wrong.
Gauss didn't specify how he solved the problem so quickly. Mathematical historians tend to think that Gauss had mastered arithmetic progression's summation method at that time. For a child as young as 10, it is unusual to discover this mathematical method independently. The historical facts described by Bell according to Gauss's own account in his later years should be more credible. Moreover, it can better reflect the characteristics that Gauss paid attention to mastering more essential mathematical methods since he was a child.
reference data
Gauss Sum _ Baidu Encyclopedia