Question

Find the sum of the first $11$ terms of the A.P: $2,6,10,14,....$

Answer 1

There are two formulae to find the sum of the terms of an $AP$.

In this case we know the following:

$a=2,d=4,n=11$

$S_n=\frac{n}{2}[2a+(n-1\left)d\right]$

$S_{11}=\frac{11}{2}\left[2\right(2)+(10\left)4\right]$

$S_{11}=5.5[4+40]$

$S_{11}=242.$