Question

Sum of first 20 terms of the series $-10,-8,-6,\dots \dots$ is :

• A. $-580$
• B. $180$
• C. $200$
• D. $-600$

Answer 1

Answer: (B)

first term $a=10$, common difference $d=2$
$S_{20}=\frac{20}{2}[-20+(20-1)(2)]=180$