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|dw:1354171632278:dw|

is the answer 20?

it similar by :
3(1) + 3(2) + 3(3) + 3(4) + ... + 3(10)
= 3(1+2+3+4+...+10)
= ......

so im wrong, i thought you were supposed to use the formula, Sn=n(a1+an)/2

yea there are about 8 questions that are under that two part question

Your formula would work; you must have done it wrong.

\[S_{n} = \frac{n}{2} (a_{1} + a_{n})\]
Did you use 10 for \(n\) and 3 for \(a_{1}\)?

for n, i put 10, a1, i put 1, and for A n, i put 3

i got 75, am i right?

No. What is your calculation?

|dw:1354172733466:dw|

Why are you using 10 for \(a_{n}\)?

It wants \(a_{n}\), not \(n\).

|dw:1354173323720:dw|

That looks great.

ughhh finally!

so i get 330/2=165

Yup. :)