## Precalculus (6th Edition) Blitzer

The sum of an arithmetic sequence is given by: $S_n=\dfrac{n}{2}[a_1+a_n]$ and the nth term for an arithmetic sequence is given by $a_n=a_1+(n-1) d$ Here, $a_1 \to$ Initial Term = 6 h 45 minutes and $d=$ Common difference= 23 minutes Now, the stopping time for the nth bus is: $a_n=6 h 45 minutes+23 (n-1)$ Thus, the given statement makes sense.