The 4th term of a GP is 81 and the first term is 3. Find the common ratio.

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Accepted Answer

1. Let the first term be $a=3$ and common ratio be $r$.
2. The 4th term is $a r^{3}$, so $3r^{3}=81$.
3. Divide both sides: $r^{3}=27$.
4. Take cube root: $r=3$.

FINAL_ANSWER: b

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