Find the sum of the first n terms of the following arithmetic sequence.
-$$a _ { 1 } = 5 , d = 5 ; \quad n = 4$$
A) 50
B) 20
C) 15
D) 25

Question

Quizplus · Accepted Answer

The sum of the first n terms of an arithmetic sequence is given by the formula $ S_n = \frac{n}{2} (2a_1 + (n-1)d) $. Substituting the given values: $ S_4 = \frac{4}{2} (2 \times 5 + (4-1) \times 5) = 2 \times (10 + 15) = 2 \times 25 = 50 $.

Find the Sum of the First N Terms of the Following