Question

The first term of a g.p. is 27 and 8th term is 1/81. find the sum of its first 10 terms.

Answer 1

heya.......

Let GP=a,ar,...,arn−1

As you mention first term is a=27,and  a8=1/81

a8=ar^7=1/81

(3^3)∗r^7=1/3^4

r=(1/3^7)1/7=1/3

Using sum of GP. form.

Sn=a(1−rn)/1−r

S10=27(1−(1/3)^1 0)/1−(1/3)

S10=40.5

tysm.....#gozmit

Answer 2

Answer: 81 / 2 ( 1 - 1 / 3 ^10)

Step-by-step explanation:

Please see the attached picture.