Question

For an A.P., find S₇ if a = 5 and d = 4.

Answer 1

a = 5, d = 4

`S_n = n/2[2a +(n -1)d]`

`S_7 = 7/2[2(5) + (7 - 1)(4)]`

`= 7/2 [10 + 24]`

`= 7/2 xx 34`

S₇ = 119