SOLUTION: Find the sum of the first 12 terms of the arithmetic sequence given by: an (the n after the a is small at sets to the lower right side of the a) =5n. a. 391 b.780 c.390 d.360

SOLUTION: Find the sum of the first 12 terms of the arithmetic sequence given by: an (the n after the a is small at sets to the lower right side of the a) =5n. a. 391 b.780 c.390 d.360

Algebra.Com

Question 880626: Find the sum of the first 12 terms of the arithmetic sequence given by: an (the n after the a is small at sets to the lower right side of the a) =5n.
a. 391
b.780
c.390
d.360
Answer by richwmiller(17219) (Show Source): You can put this solution on YOUR website!
S = �(2A1 + (n-1)d)n
where A1=5
d=5
n=12
S = �(2*5 + (11)5)12
S=6*(10+55)
S=6*65=390

RELATED QUESTIONS
The sum of the first n terms of an arithmetic squence is given by the formula; Sn= n/2... (answered by edjones)

The sum of the first n terms of an arithmetic sequence is (2n^2)-n. Find the general term (answered by MathLover1)

Prove that a sequence is arithmetic Q: The sum of the first n terms of a progression is (answered by richard1234)

Find the sum of the first 12 terms of the arithmetic sequence given by: an=5n a. 391... (answered by ewatrrr)

Find the sum of the first 12 terms of the arithmetic sequence whos general term is an=3n+ (answered by dkppathak)

Find the sum of the first 12 terms of the arithmetic sequence whos general term is an=3n+ (answered by dkppathak)

An arithmetic sequence of 15 terms has a sum of 3060. The common difference and each... (answered by greenestamps)

The sum of the first n terms of an arithmetic sequence is n(3n + 11)/2 . a) Find its 1st (answered by Fombitz)

2. Given that (4 20) 2 n + n is the sum of the first n terms of an arithmetic... (answered by greenestamps)