Chapter 11 - 11.2 - Arithmetic Sequences and Partial Sums - 11.2 Exercises - Page 786: 49

$S_{100}=10000$

Sequence of the positive odd integers: 1, 3, 5, 7, ... That is, $a_1=1$ and $d=2$ $a_n=a_1+(n-1)d$ $a_{100}=1+(100-1)2=1+(99)2=1+198=199$ $S_n=\frac{n}{2}(a_1+a_n)$ $S_{100}=\frac{100}{2}(1+199)=50(200)=10000$