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.

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  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 : )

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  2. Thank you!

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  3. You are most welcome!

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