Question

The common ratio of a geometric progression is 1/2 , the fifth term is 1/80 , and the sum of all of its terms is 127/320 . Find the number of terms in the progression.

Answer 1

Start by using the geometric formula with r=1/2. Sub in 1/80 as the term value and n=5, then solve for "a" the first term.
Once you have the first term, sub it and the sum of 127/320 into the sum formula and solve for n : )

Answer 2

Thank you!

Answer 3

You are most welcome!