Question

find the sum of first 20 terms of given arithmatic series. 3+5+7+9+11
please answer my question it is very urgent​

Answer 1

Answer:

$= 780$

Step-by-step explanation:

a=3

d=2

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

$\frac{20}{2} (2 \times 20 + (20 - 1) \times 2)$

$10(40 + 38)$

$10 \times 78$

$= 780$