Determine the sum of the first 20 terms of an arithmetic series with an

initial term of 3 and a common difference of 2.

440

Step-by-step explanation:

Determine the sum of the first 20 terms of an arithmetic series with an

initial term of 3 and a common difference of 2.

We have:

formula: a_n = (n - 1) d + a_1

SUM [from n = 1 to m] a_n = SUM [n=1 to m] (n - 1) d + a_1 = d * (m-1) * m/2 + m*a_1 = m * (a_m + a_1) / 2

a_20 = (20 - 1) * 2 + 3 = 19*2 + 3 = 38 + 3 = 41

a_1 = 3

so SUM [n=1 to 20] = 20 * (41 + 3) / 2 = 20 * 44/2 = 10*44 = 440