Q3 of 85 Page 104

For a given A.P. with

a = 2, d = 3, find S30.

Formula used.


Sn = [2a + (n–1)d]


d = an + 1–an


In the following A.P


⇒ a = 2,


⇒ d = 3


⇒ n = 30


Sn = [2a + (n–1)d]


= [2×2 + (30–1)3]


= 15[4 + 29×3]


= 15[4 + 87]


= 1365


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