## anonymous one year ago What is the sum of the first 18 terms of the arithmetic series 11 + 15 + 19 + 23 + ⋯? a.) 684 b.) 810 c.) 831 d.) 846

1. anonymous

is it 810 ??

2. rishavraj

u see the first term i.e a_1 = 11 and common difference i.e d = 4 and sum of "n" terms is $S_n = \frac{ n }{ 2 }(2a_1 + (n - 1)d)$