Answer
1220
Work Step by Step
The given series = 4, 10, 16, 22
Common difference d = 22 - 16 = 16 - 10 = 10 - 4 = 6
$1^{st}$ term ($a_{1}$) = 4
To solve this type question, first find the $20^{th}$ term, after that find the sum.
$20^{th}$ term = $a_{1}$ + (20 - 1) d
= 4 + 19 $\times$6
= 4 + 114
= 118
Sum of all terms = $\frac{n}{2}$($a_{1}$ + $a_{n}$)
Sum of first 20 terms = $\frac{20}{2}$(4 + 118)
= $\frac{20}{2}$(122)
= 10$\times$122
= 1220
