Each level of a smartphone app adds more gems for you to match. On level one, there were 13 gems. On level twelve, there were 123 gems. When you complete all twelve levels, how many total gems will you have matched?

Question

anonymous · Answer

605

 660

 748

 816

anonymous · Answer

Need some help applying the formula of Arithmetic Series. Don't quite understand it.

jdoe0001 · Answer

$\bf \textit{sum of arithmetic sequence}=S_n=\cfrac{n_2}{2}(a_1+a_n)\\ \quad \
n=n^{th}\textit{ term, in this case, 12}\
a_1=1^{st}\textit{ term value, in this case, 13}\
a_n=\textit{value of the }n^{th}\textit{ term, in this case, 123}$

anonymous · Answer

816