Question

I WANNA LEARN, PLEASE HELP
What is the sum of a 56-term arithmetic sequence where the first term is 6 and the last term is 391?

10,719
11,116
11,513
11,910

Answer 1

Well hello there miss.
We have this handy dandy formula for finding the sum of an arithmetic sequence if we don't want to count it out by hand,\[\large\rm S_n=\frac{n}{2}(a_1+a_n)\]It's half of the number of terms times the quantity first term plus last term.

Answer 2

So plug in your stuff, simplify,\[\large\rm n=56\qquad\qquad a_1=6\qquad\qquad a_{56}=391\]

Answer 3

sum = (total terms/ 2)*(fist term + last term) =>
(56/2)*(6+391) => 28*(397) =11116

Answer 4

what happened? @destinykiara99