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Question
Find the sum of the following geometric progression:
1, 3, 9, 27, ... to 8 terms;
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Solution
Here, a = 1 and r = 3.
\[\therefore S_8 = a\left( \frac{r^8 - 1}{r - 1} \right) \]
\[ = 1 \left( \frac{3^8 - 1}{3 - 1} \right) \]
\[ = \frac{6561 - 1}{2}\]
\[ = 3280\]
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