Given A.P in which a = 17
Last term = l = 350
Common difference, d = 9
We know that, an = a + (n – 1) d
350 = 17 + (n- 1) 9
⇒ 350 = 17 + 9n – 9
⇒ 9n = 350 – 8
⇒ n = \(\frac{342}{9}\) = 38
Now, Sn = \(\frac{n}{2}\)(a + l)
S38 = \(\frac{38}{2}\)(17 + 350)
= 19 × 367 = 6973
∴ n = 38; Sn = 6973