Question

find the sum of first twenty terms of arthmetic series 2+7+12....using formula​

Answer 1

Hope this answers the question

Answer 2

$sn = \frac{n}{2} {2a + (n - 1)d}$

$s20 = \frac{20}{4} \: (4 + 95)$

$s20 = 5 \times 99$

$s20 = 990$