Question

PLEASE HELP will medal!!!

What is the sum of the arithmetic series below? Use the formula for the sum of an arithmetic series.

Answer 1

as the questions says, do u have the formula for sum of arithmetic series ?

Answer 2

I do not like this series thing. I don't understand it. No I don't have the formula. The sigma or whatever always throws me off.

Answer 3

sorry
(2a+(n-1)*d)*n/2

Answer 4

@minoz why did you say that a = 10 above, isn't it 8 ?

Answer 5

I really don't need to get any more wrong answers.
Is what you have right @minoz ?

Answer 6

look buddy the answer is D 486, there's something wrong with minoz's formula above so I did it manually for u

Answer 7

by substituting in (2a+(n-1)*d)*n/2
u get 486

Answer 8

only if u have the right a and n

Answer 9

use wolfram if u want just the answer, you dont need 3-4 ppl's time to provide u wid just the answer :
http://www.wolframalpha.com/input/?i=%5Csum+%5Climits_%7Bi%3D1%7D%5E%7B18%7D+2i%2B8

Answer 10

Sum to n terms in AP is the above formula
first i mentioned it wrong and then corrected myself

Answer 11

http://www.wolframalpha.com/input/?i=%5Csum+%5Climits_%7Bi%3D1%7D%5E%7B18%7D+%282i%2B8%29

Answer 12

@kx2bay is right ! you should get 486 if u add them all

Answer 13

a is the first term
and d is common difference
by substituting i=1, u get 2(1)+8=10
then d is difference between any two succeding terms
second term is 2(2)+8=12
then d=12-10=2
n=total terms=18

Answer 14

ok @minoz I'm going to use your formula now and test it, tell me please the following
n=?
a=?
d=?
what values should the above be so as to get an answer of 486?

Answer 15

here the series is expanded ad 2(1)+8,2(2)+8,2(3)+8,.......2(18)+8=10,12,14,...44
which is an arithmetic progression
n is total i values, given i=1,2,..18
so n=18 terms
a is first term which we get by substituting i=1 in the expression
a=2i+8=2(1)+8=10
a=10
d=second term-first term
=2(2)+8-(2(1)+8)=12-10=2


so n=18
a=10
d=2

Answer 16

formula is (2a+(n-1)d)*n/2 @kx2bay

Answer 17

correct
sorry @minoz
I WAS an IDIOT - got misguided by the formula on this site
http://www.mathsisfun.com/algebra/sequences-sums-arithmetic.html
where based on that n and a will be different but their formula is exactly like yours just different k, a, n
my appologies

Answer 18

its ok i dont mind anything
we are here to solve our doubts
:)

Answer 19

Look at that you both got medals happy days

Answer 20

we should give you one too to make the days even happier ;)

Answer 21

:D