(Q19).In an AP:
(i) Given a = 5, d = 3, a
n
= 50. find n and S
n
.
Given :
a =
; d =
;
a
n
= a + (n – 1)d = 50
⇒
=
+ (n – 1)
⇒
–
=
n –
⇒
n =
+
⇒ n =
=
Now, S
n
=
n
2
(a + l)
S
16
=
2
(
+
)
=
×
=
Clear