Question

Find the indicated nth partial sum of the arithmetic sequence.

1.6, 4.2, 6.8, 9.4, ..., n = 50

Answer 1

+2.6 ?

Answer 2

The nth term = dn + c.
I think I use this to solve but when I do none of my answers match up with my choices

Answer 3

and yes 2.6 is the common difference (d)

Answer 4

1.6 + 2.6(n) ?? think I am wrong...

Answer 5

my answer choices are:
A. 2090
B.3395
C.3265
D.3266
E.3264

Answer 6

would it not be 1.6+2.6(n-1) ?? Remembering that you start at n=1

Answer 7

math: thats what I thought, but doubted myself....

Answer 8

Well thats what I was doing but as you can see none of my answer choices match that answer

Answer 9

that's because you are looking for the sum of the terms up o the 50th term

Answer 10

ohhhh wow silly me so I have to go back and add them all up.... sorry about that

Answer 11

the idea of the question i assume is for you to find the formula which does the sumation for you

Answer 12

can you do that with an integral of the equation?

Answer 13

i think to find n, you could use 50=n/2 (1.6+(n-1)2.6)

Answer 14

no because that would find the area under an axis of real numbers whereas you are looking to sum natural numbers

Answer 15

\[s \left[ n \right]=n\2(a \left[ 1 \right]+a \left[ n \right])\]

Answer 16

maybe?

Answer 17

no I don't think that is right either.....

Answer 18

no its not, keep trying though

Answer 19

Just kidding I figured it out the answer is c

Answer 20

1.6+49(2.6)=129
50/2(1.6+129)=3265

Answer 21

oh i see what you meant now by your notation! My mistake, well done :)

Answer 22

do any of you know or understand how to figure out a problem like this:
Find the sum of the infinite series:
\[\sum_{i=1}^{\infty}2(-1/4)^i\]

Answer 23

Thanks It took me a sec to think through it and figure it out lol maybe if I had originally read the question better lol :)

Answer 24

if i remember correctly there is a formula for the sum of an infinite series, first take 2 out as it is a constant and then apply the formula, (try wikipedia for it because i cannot be sure of my memory). As -1<r<1 you can use the formula where r=-1/4

Answer 25

Ok thanks