The first and the last terms of an A.P. are 17 and 350 respectively. If the common difference is 9, how many terms are there and what is their sum?
a = 17, l = 350, d = 9
Number of terms, n = 
+ 1
= 
+ 1
= 
= 
= 38
Sn= 
(a + l)
= 
(350 + 17)
= 19 (367) = 6973
6