The first and the last terms of an AP are 17 and 350 respectively. If the common difference is 9, how many terms are there and what is their sum?

Given first term (a) = 17, last term (a_n) = 350

Common difference (d) = 9

a_n = a + (n-1) d

350 = 17 + (n-1) 9

333 = 9(n-1)

37 = n-1

n = 38.

Sum of the series (s_n) = [2a + (n-1) d]

= ( 2×17 +(38-1)9)

= 19 × 367

= 6973