Question

What is the sum of the first $40$ even positive integers?

• A. $1600$
• B. $1560$
• C. $820$
• D. $1640$
• E. $400$

Answer 1

The correct option is D $1640$

According to problem:

$a=2,$ First term

$d=2,$ common difference

$n=40,$ number of terms

$\because S_n=\frac{n}{2}[2a+(n-1\left)d\right]=1640$

$⟹S_n=\frac{40}{2}[2\times 2+(40-1\left)2\right]=1640$