What is the sum of the first five terms of a geometric series with a1 = 10 and r = 1/5?

Express your answer as an improper fraction in lowest terms without using spaces.

Question

Conner Best

Mathematics

8 May, 22:13

What is the sum of the first five terms of a geometric series with a1 = 10 and r = 1/5?

Express your answer as an improper fraction in lowest terms without using spaces.

+2

Answers (2)

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Raelynn · Answer 1

A 1 = 10

a 2 = 10 * 1/5 = 2

a 3 = 2 * 1/5 = 2/5

a 4 = 2/5 * 1/5 = 2/25

a 5 = 2/25 * 1/5 = 2/125

S 5 = a 1 + a 2 + a 3 + a 4 + a 5 = 10 + 2 + 2/5 + 2/25 + 2/125 =

= 1250/125 + 250/125 + 50/125 + 10/125 + 2/125 = 1562 / 125

Dawson Moss · Answer 2

Formula : Sn=a1 (1-r^n) / 1-r

S5=10 (1-1.5^5) / 1-1.5

10 (1-7.8) / - 0.5

10 (-6.8) / - 0.5

-68/-0.5 = 136

What is the sum of the first five terms of a geometric series with a1 = 10 and r = 1/5?Express your answer as an improper fraction in lowest terms without using spaces.

What is the sum of the first five terms of a geometric series with a1 = 10 and r = 1/5?

Express your answer as an improper fraction in lowest terms without using spaces.