Question

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

Options

• 5240

• 2620

• 1310

• 2680

Answer 1

The sum of 40 terms of the A.P. 7 + 10 + 13 + 16 + .......... is 2620.

Explanation:

For given A.P, a = 7; d = 10 – 7 = 3

We know that

`S_n = n/2 [2a + (n - 1)d]`

∴ `S_40 = 40/2 [2 xx 7 + (40 - 1)3]`

= 20[14 + 117]

= 20 × 131

= 2620