Find the sum of each of the following APs: 2, 7, 12, 17, ... to 19 terms.

Question

Philoid · Accepted Answer

Here, first term = 2

Common difference = 7 - 2 = 5

Sum of first n terms of an AP is

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

∴ S₁₉ = [2(2) + (19 - 1)5]

= (19)(4 + 90)/2

= (19 × 94)/2

= 893

Thus, sum of 19 terms of this AP is 893.