#### Answer

$77.5$

#### Work Step by Step

$S_{n}=\dfrac {a_{1}+a_{n}}{2}\times n=\dfrac {10+5.5}{2}\times 10=77.5$

Published by
Pearson

ISBN 10:
013421742X

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

$77.5$

$S_{n}=\dfrac {a_{1}+a_{n}}{2}\times n=\dfrac {10+5.5}{2}\times 10=77.5$

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