Question 388210
1+2+3+4+5+...+30 = {{{(30/2)(1+30) = 15*31 = 465}}}.
This answer comes from the formula {{{S_n = (n/2)(a_1+a_n)}}}, where
a_1 = 1st term of the sequence,
a_n = nth term of the sequence, and S_n = sum of the 1st to the nth terms.