The sum of 40 terms of the A.P. 7 + 10 + 13 + 16 + ….. is :

1. 5240

2. 2620

3. 1310

4. 2680

In the A.P., 7 + 10 + 13 + 16 + ………

First term (a) = 7

Common difference (d) = 10 - 7 = 3.

By formula,

Sum of n terms = $\dfrac{n}{2}[2a + (n - 1)d]$

Sum of above A.P. (upto 20 terms)

$= \dfrac{40}{2}[2 \times 7 + (40 - 1) \times 3] \\[1em] = 20 \times [14 + 39 \times 3] \\[1em] = 20 \times [14 + 117] \\[1em] = 20 \times 131 \\[1em] = 2620.$

Hence, Option 2 is the correct option.