#### Answer

0.6309

#### Work Step by Step

From the change of base formula, we know that $log_{b}a=\frac{log_{c}a}{log_{c}b}$ ($a$, $b$, and $c$ are positive real numbers and neither $b$ nor $c$ is equal to 1).
Therefore, $log_{9}4=\frac{log_{10}4}{log_{10}9}=\frac{0.6021}{0.9542}=0.6309$.