9. Which integer $n$ satisfies $\frac{3}{10}<\frac{n}{20}<\frac{2}{5}$ ?
A 3
B 4
C 5
D 6
E 7
9. E We are given that $\frac{3}{10}<\frac{n}{20}<\frac{2}{5}$. Therefore $\frac{6}{20}<\frac{n}{20}<\frac{8}{20}$. So, as $n$ is an integer, $n=7$.