#### Answer

$155$

#### Work Step by Step

$a_{1}=5;r=\dfrac {40}{20}=\dfrac {20}{10}=\dfrac {10}{5}=2\Rightarrow S_{n}=\dfrac {a_{1}\left( 1-r^{n}\right) }{1-r}=\dfrac {5\times \left( 1-2^{5}\right) }{1-2}=155$

Published by
Pearson

ISBN 10:
013421742X

ISBN 13:
978-0-13421-742-0

$155$

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