Answer
$121$
Work Step by Step
$\sum ^{5}_{i=1}81\left( \dfrac {1}{3}\right) ^{i-1}=\dfrac {a_{1}\left( 1-rn\right) }{1-r}\Rightarrow a_{1}=81\left( \dfrac {1}{3}\right) ^{1-1}=81;r=\dfrac {1}{3}\Rightarrow S5\dfrac {81\left( 1-\left( \dfrac {1}{3}\right) ^{5}\right) }{1-\dfrac {1}{3}}=\dfrac {81\left( \dfrac {242}{243}\right) }{\dfrac {2}{3}}=121$
