Question

For the arithmetic series 1/3+4/3+7/3+.... determine S7

Answer 1

S7 = 70/3

Explanation:

Given:

series: 1/3+4/3+7/3+....

a = 1/3

Find:

S7

Computation

d = a2-a1

d = 4/3 - 1/3

d = 1

⇒ Sn = n/2[2a+(n-1)d]

⇒ S7 = 7/2[2(1/3)+(7-1)1]

⇒ S7 = 7/2[2/3+6]

⇒ S7 = 7/2[20/3]

S7 = 70/3