Answer
1010
Work Step by Step
$S_{n}=\dfrac {n}{2}\left( 2a+\left( n-1\right) d\right) =\dfrac {20}{2}\left( 2\times 3+\left( 20-1\right) \times 5\right) =10\left( 6+95\right) =1010$
Precalculus: Mathematics for Calculus, 7th Edition
by Stewart, James; Redlin, Lothar; Watson, Saleem
Published by
Brooks Cole
ISBN 10:
1305071751
ISBN 13:
978-1-30507-175-9
Chapter 12 - Section 12.2 - Arithmetic Sequences - 12.2 Exercises - Page 857: 51
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