The first term of an A.P is 2 and it's common difference is 3, find the sum of the first 11 terms of the A.P

Answer 1

S11 = 11/2 (2a+10d)
so plug and chug

Answer 2

The sum of the first n terms of the A.P :

S(n) = n / 2 [ 2 a1 + ( n - 1) d ]

In this case:

a1 = 2 , d = 3 , n = 11

S(11) = 11 / 2 [ 2 ∙ 2 + ( 11 - 1 ) ∙ 3 ]

S(11) = 5.5 ( 4 + 10 ∙ 3 )

S(11) = 5.5 ( 4 + 30 )

S(11) = 5.5 ∙ 34

S(11) = 187