MCQ
$(5+13+21+\ldots .+181)=$ ?
- A$2476$
- B$2337$
- C$2219$
- ✓$2139$
✓
Answer
Correct option: D.
$2139$
Let the number of terms be $n$.
$\text {Then, } T_{n}=181$
$\therefore 5+(n-1) \times 8=181$
$\Rightarrow(n-1) \times 8=176 $
$\Rightarrow n-1=22 $
$\Rightarrow n=23$
$\therefore \text { Sum }=\frac{n}{2}(a+l)$
$=\frac{23}{2}(5+181)$
$=23 \times 93$
$=2139$
$\text {Then, } T_{n}=181$
$\therefore 5+(n-1) \times 8=181$
$\Rightarrow(n-1) \times 8=176 $
$\Rightarrow n-1=22 $
$\Rightarrow n=23$
$\therefore \text { Sum }=\frac{n}{2}(a+l)$
$=\frac{23}{2}(5+181)$
$=23 \times 93$
$=2139$
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