Chapter 10 - Section 10.2 - Arithmetic Sequences - Exercise Set - Page 1061: 71

$2869$ Seats

We know that $a_n=a_1+(n-1) d$ Here, we have $a_1=20$ and $d=3$ and $a_{38}=20+3(38-1)=131$ The sum of an arithmetic sequence is given by: $S_n=\dfrac{n}{2}[a_1+a_n]$ $S_{38}=\dfrac{38}{2}[20+131]=2869$ Seats