Chapter 3 - Polynomial and Rational Functions - Chapter 3 Test Prep - Review Exercises - Page 402: 89

$s=0.75$.

Step 1. As t varies inversely as s, we have $t=\frac{k}{s}$ where $k$ is a constant. Step 2. As $t=3$ when $s=5$, we have $3=\frac{k}{5}$, thus $k=15$ Step 3. For $t=20$, we have $20=\frac{15}{s}$, thus $s=0.75$.