Question

find the sum of AP
10+ 14+ 18......104​

Answer 1

a = 10

l = 104

d = 4

n=?

an= a+(n-1)d

104= 10 +(n-1)4

104/4 -10 =n-1

n-1 = 26 -10

n = 16 + 1 = 17

now sum of first 17 terms is

Sn = n/2(a+l)

S17 = 17 / 2 x (10 + 104)

S17 = 17 / 2 x 114

S17 = 17 x 57

S17 = 969= Answer