Question

Find the sum of 1st 30 terms of an ap whose 2nd term is 2 and 7th term is 22

Answer 1

a2 = 2
a7 = 22
a+d = 2
a+6d = 22
By elimination method, we get 5d = 20
d = 4
a = -2
Sum of 30 terms =
30/2 {2a + (n-1)d}
15 {2 (2 (-2)+(29*4)}
15 {-4 + 116}
15*112
1680 = Ans