Question

HELP! Please? So CONFUSED! Math hates me. :(

Did I do it right?

What is the sum of the first five terms of a geometric series with a1 = 6 and r = 1/3?
Express your answer as an improper fraction in lowest terms.

6(1-1/3^5) 6(1-1/243) 6(242/243)
s5 = --------- = ------- -------
1 - 1/3 2/3 2/3
484/81 242
------ = ----
2/3 27

s5 = 242/27

Answer 1

at the end I do 484/81 divided by 2/3 and get 242/27

but when I do 484/81 divided by 1-1/3 I get 457/81

Which one is correct?

Answer 2

in your calculator is it

Answer 3

1-(1/3)

Answer 4

or 1-1/3

Answer 5

it's supposed to be 1- 1/3, like that's what it is in the formula

Answer 6

Yeah enter it in as 1-(1/3) not as 1-1/3 because your calculator thinks its (1-1)/3 I'm guessing

Answer 7

Because take away 3/3 -1/3 and you get 2/3 which is right

Answer 8

so the answer is 242/27?

Answer 9

yup

Answer 10

Yes. 242/27.

You can check your answer by this route also:

6 + 2 + 2/3 + 2/9 + 2/27 = 8 & 26/27 = 242/27