12. What is the sum of the finite arithmetic series?

Question

(–5) + 0 + 5 + 10 + ... + 65

Answer 1

answer options
900
455
450
445

Answer 2

the common difference is 5

there are 15 terms

[65 + (-5)] * 15/2 = ?

Answer 3

65+ (-5)=60
15/2=7.5
7.5*60=450

okay, i get it now, thanks!