Question

what is the sum of 1+2+3+...+385

Answer 1

\[\Large 1+2+....+n=\frac{ n(n+1) }{ 2 }\]

Answer 2

what number is n?

Answer 3

n=385

Answer 4

Yes, whatever the last number of the summation is. In your problem, it is 385. It's a general formula for the total of a sum of integers from 1 to any integer n. :)