Question

I'll FAN & MEDAL!!
What is the sum of the first eight terms of a geometric series whose first term is 3 and whose common ratio is 1/2 ?

Answer 1

my connection has been very bad lately. finally got to the thread;)

Answer 2

For a geometric sequence, starting from the first term \(a1\) and a common ratio \(\rm r\),
the sum for \(\rm n\) number of terms (in the sequence) is given by the following formula.

\(\large\color{black}{ \displaystyle {\rm S}_{\rm n}=\frac{a_1\times \left(1-{\rm r}^{\rm n}\right) }{1-{\rm r}} }\)

Answer 3

You need to add 8 terms, so your n is 8.
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Your common ratio is ½, so r=½.
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And your first term is 3, so \(a_1\)=3
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Answer 4

Just plug this information into the formula, and calculate.

Good luck:)