Question

What is the sum of the arithmetic sequence 3, 9, 15…, if there are 22 terms?

a. 2,268
b. 2.028
c. 1,452
d. 1,728

Answer 1

Actually, it's
\[S_{n} = \frac{n}{2}(2a_{1} + [n - 1]d)\]

Answer 2

Sn = 22 / 2 (2(3) + [22 - 1]6)

Solve.

Answer 3

Sn = 22 / 2 (2(3) + [22 - 1]6)
Sn = 11 (6 + [21]6)
Sn = 11 (6 + 126)
Sn = 11 (132)
Sn = 1452

So C. 1452 is your answer. :)
And thankyou @Calcmathlete for the formula. :)

Answer 4

lol. Just takes some memorization :) Btw, what grade are you in @JBrightman3 and what level math?

Answer 5

I'm going into 9th grade when school starts again, but I am doing highschool honors calculus. :)

Answer 6

What about you?

Answer 7

That is the answer I got. Thank y`all (:

Answer 8

Woah. Calculus? Can't believe that...
I'm done with Algebra II and am going to Advanced Pre-calculus 10th Grade this fall.

Answer 9

np :)

Answer 10

No problem Tiffani. And that's cool Calcmathlete. Are you in FLVS?

Answer 11

I was for Algebra II, but I'll be doing classes not math related.

Answer 12

From now on anyway :)

Answer 13

Ya`ll are in lower grades than me, but definitely waaay smarter! Haha (:

Answer 14

lol. Is FLVS why you're at such a high level of math?

Answer 15

Well last year was my first year of FLVS, I was homeschooled by my mom since 2nd grade, so I have her to thank! :)

Answer 16

Ok. I know VERY few people that are at such a high level of math in 9th grade. Good Job :)