The mean of numbers in A.P. 2, 4, 6, 8, ……, 40 is :

1. $\dfrac{40 + 2}{2}$

2. $\dfrac{20}{2}(2 + 40)$

3. $\dfrac{10}{2}$ (2 + 40)

4. 840

Given,

A.P. : 2, 4, 6, 8, ……, 40

a = 2, d = 2.

In an A.P.,

⇒ a_n = a + (n - 1)d

⇒ 40 = 2 + 2(n - 1)

⇒ 40 - 2 = 2(n - 1)

⇒ 38 = 2(n - 1)

⇒ n - 1 = $\dfrac{38}{2}$

⇒ n - 1 = 19

⇒ n = 19 + 1

⇒ n = 20.

Sum of A.P. = $\dfrac{n}{2}(a + l) = \dfrac{20}{2}(2 + 40)$.

Hence, Option 2 is the correct option.