Question

What is the sum of the first 28 terms of this arithmetic sequence?

69, 75, 81, 87, 93, 99, …




A. 2,436




B. 4,200




C. 4,320




D. 4,368

Answer 1

B

Answer 2

I actually wrote them all down, sorry.

Answer 3

\[S_n=\frac{n(a_1+a_n)}{2}\]
Sn is the sum of the first n terms
a1 is the first term
an is the nth term

Answer 4

you can find the 28 term by using:
\[a_n=a_1+d(n-1) \\ a_{28}=69+d(28-1)\]
I will let you say what d is

Answer 5

THANKS