Question:
Find the sum of the series 2 + 5 + 8 + 11 + …. + 191.
Solution:
To Find: The sum of the given series.
The nth term of an AP series is given by
$t_{n}=a+(n-1) d$
$\Rightarrow 191=2+(n-1) 3$
$\Rightarrow 3(n-1)=189$
$\Rightarrow n-1=63$
$\Rightarrow n=64$
Therefore,
$S_{n}=\frac{n}{2}[2 a+(n-1) d]$
$S_{n}=\frac{64}{2}[4+63 \times 3]$
= 32 × 193 = 6176
The sum of the series is 6176.