This is the question 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9. + 100 =?

This is the question 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9. + 100 =?

I'm glad to answer your question!
answer
Classmate, this is a classic topic, obtained by the mathematics champion Gauss
The way to get to the problem is to add the reciprocal, that is, to invert the formula
100+99+98…… +3+2+1=
1+2+3+…… +98+99+100=
Look at these two formulas and add them up to 101 + 101 + 101 + +101 + 101 + 101 =, there are 100 101 in total, that is 101 * 100, but this is the sum of the two formulas, regardless of dividing by 2, that is 101 * 100 / 2 = 5050
Deduce the formula: S = n * (n + 1) / 2 (n is mantissa)
I hope my answer can satisfy you