Question

If the first term of an AP is $5$ and the common difference is $-2,$ then the sum of the first $6$ terms is

• A. $0$
• B. $5$
• C. $6$
• D. $15$

Answer 1

The correct option is A $0$

Sum of an AP is: $\frac{n}{2}\times \left[2a+(n-1)d\right]$
$a=5,d=-2,n=6$

Sum $=\frac{6}{2}\times \left[(2\times 5)+(6-1)\times (-2)\right]$

$=3\times (10-10)$
$=0$