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Nerdgirl
 one year ago
Find the sum of the following series.
(shown below)
A. 240
B. 255
C. 210
D. 510
Nerdgirl
 one year ago
Find the sum of the following series. (shown below) A. 240 B. 255 C. 210 D. 510

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Nerdgirl
 one year ago
Best ResponseYou've already chosen the best response.0dw:1434376110688:dw

Nerdgirl
 one year ago
Best ResponseYou've already chosen the best response.0@aloud that's not one of my answers @phi PLEASE HELP!

Nerdgirl
 one year ago
Best ResponseYou've already chosen the best response.0no you ditz it's not one of them don't you get it?! it's not one of the answer choices!

phi
 one year ago
Best ResponseYou've already chosen the best response.3rewrite the problem \[\sum_{1}^{15}(2n+1)= 2\sum_{1}^{15}n+\sum_{1}^{15}1\]

phi
 one year ago
Best ResponseYou've already chosen the best response.3There is a formula to add up the numbers from 1 to n do you know it? and the second sum means add up 15 1's (which hopefully you know how to do)

Nerdgirl
 one year ago
Best ResponseYou've already chosen the best response.0Mmm.... what would you say if I said I knew it but I couldn't remember it? :p

phi
 one year ago
Best ResponseYou've already chosen the best response.3Gauss (famous mathematician), when a young kid in school was given the problem of adding up the numbers from 1 to 100, and he (clever fellow) saw a way to do it quickly. \[\sum_{k=1}^{n}k= \frac{ n(n+1) }{ 2 }\]

phi
 one year ago
Best ResponseYou've already chosen the best response.3your problem has n=15 so use that formula with n=15 and n+1 = 16

Nerdgirl
 one year ago
Best ResponseYou've already chosen the best response.0so it would be 15 (greek symbol) k=1 (1) = 15 (16)/2? @phi

phi
 one year ago
Best ResponseYou've already chosen the best response.3the sum of the numbers 1 to 15 is 15*16/2 = 15*8= 120 \[ \sum_{1}^{15}(2n+1)= 2\sum_{n=1}^{15}n+\sum_{n=1}^{15}1 \\ = 2(120) + \sum_{1}^{15}1 \] the sum of 15 ones is 15*1= 15 thus \[ \sum_{1}^{15}(2n+1)= 2\sum_{n=1}^{15}n+\sum_{n=1}^{15}1 \\ = 2(120) + 15 \] can you finish?

Nerdgirl
 one year ago
Best ResponseYou've already chosen the best response.0OMG ILY THANK YOU!!!!!!!!!!!
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