## Precalculus (6th Edition) Blitzer

$6480$
Formula to calculate the sum of an arithmetic sequence is: $S_n=\dfrac{n}{2}(a_1+a_n)$ ...(1) Here, $a_1:$ First term and $a_n=$last term and $a_1:$ First term is 2 and $a_n$:last term is 160 Then, our first (1) equation becomes: $S_{80}=\dfrac{80}{2}(2+160)\\=40(162)\\=6480$