已知\(\{a_{n}\}\)是首项为\(1\)的等比数列，\(S_{n}\)是其的前\(n\)项和，且\(9S_{3}=S_{6}\)，则数列\(\{ \dfrac {1}{a_{n}}\}\)的前\(5\)项和为\((\)　　\()\) --优优班--学霸训练营

已知\(\{a_{n}\}\)是首项为\(1\)的等比数列，\(S_{n}\)是其的前\(n\)项和，且\(9S_{3}=S_{6}\)，则数列\(\{ \dfrac {1}{a_{n}}\}\)的前\(5\)项和为\((\)　　\()\)

A．\( \dfrac {15}{8}\)或\(5\)

B．\( \dfrac {31}{16}\)或\(5\)

C．\( \dfrac {31}{16}\)

D．\( \dfrac {15}{8}\)

【考点】等比数列的求和,等比数列的性质

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难度：较易

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