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LilyMQ
 one year ago
What is the sum of a 23term arithmetic sequence where the first term is 9 and the last term is 119?
LilyMQ
 one year ago
What is the sum of a 23term arithmetic sequence where the first term is 9 and the last term is 119?

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LilyMQ
 one year ago
Best ResponseYou've already chosen the best response.1Is it 1472? That's what I got

Jhannybean
 one year ago
Best ResponseYou've already chosen the best response.1First define what an arithmetic sum is.

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.2i think you are a little off

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.2\(\large\color{black}{ \displaystyle a_9=9 }\) \(\large\color{black}{ \displaystyle a_{23}=119 }\) \(\large\color{black}{ \displaystyle {\rm S}_{239}=\frac{\left(a_9+a_{23}\right)}{2} \times(239) }\) \(\large\color{black}{ \displaystyle {\rm S}_{239}=\frac{\left(9+199\right)}{2} \times(239) }\)

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.2where 239 is the number of terms, and the first fraction is the average term

Jhannybean
 one year ago
Best ResponseYou've already chosen the best response.1That is, \[\large S_n=\frac{n(a_1+a_n)}{2}\]To find \(a_n\) we need to use an arithmetic sequence, \(a_n = a_1 +(n1)d\)

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.2we know the 23rd term, Jhanny....

Jhannybean
 one year ago
Best ResponseYou've already chosen the best response.1Yeah I just reread it haha

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.2i think all you need is last+first term \(a_{23}\) and \(a_9\) in this case....

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.21456 is right....

Jhannybean
 one year ago
Best ResponseYou've already chosen the best response.1but whats with the multiplication?

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.2multiplication ?

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.2(9+199)÷2 => the average term 239 = number of terms (9+199)÷2 • (239) = the sum of all terms together

Jhannybean
 one year ago
Best ResponseYou've already chosen the best response.1\[\large S_{23} = \frac{23(9+119)}{2}\]

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.2you don't add the terms before \(a_9)

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.2what the hell am I saying....Jhanny, i am a laborer before thee

Jhannybean
 one year ago
Best ResponseYou've already chosen the best response.1You wrote 199 instead of 119 O_o

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.2i read \(a_9\) with my blind eyes.

Jhannybean
 one year ago
Best ResponseYou've already chosen the best response.1and @LilyMQ I have no idea. No calculator here, just helping you understand the format :)

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.29 is the 1st term... then it is completely off....

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.2(9+199)÷2 => the average term 23 = number of terms (9+199)÷2 • 23 = the sum of all terms together

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.2sorry for my mistake.

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.2yes, this is correct

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.2and this time, it is correct for real:D

LilyMQ
 one year ago
Best ResponseYou've already chosen the best response.1That doesn't make sense. These are the options 1,219 1,472 1,725 1,978

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.2the first term is 9 the last (i.e. 23rd) term is 199 are you sure about this information ?

LilyMQ
 one year ago
Best ResponseYou've already chosen the best response.1What is the sum of a 23term arithmetic sequence where the first term is 9 and the last term is 119?

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.2oops my fault again, i will try to, if i can, to refrain from my mistake

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.2i will recorrect my post again. tnx for catching the err.

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.2(9+119)÷2 => the average term 23 = number of terms (9+119)÷2 • 23 = the sum of all terms together

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.2u were correct initially....

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.2You are like :O and I am like Oh..... my fault, lol

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.2thank YOU for catching it.... with me you would have gone into the forest of unnecessary wonders.
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