To find \(\log_4(16 \cdot 64)\), we can apply the rule \(\log_b(xy) = \log_b x + \log_b y\).
First, we can express the log as:
\[ \log_4(16 \cdot 64) = \log_4(16) + \log_4(64) \]
Now, we calculate \(\log_4(16)\) and \(\log_4(64)\).
-
For \(\log_4(16)\):
- Since \(16 = 4^2\), \[ \log_4(16) = \log_4(4^2) = 2 \]
-
For \(\log_4(64)\):
- Since \(64 = 4^3\) (as \(4^3 = 64\)), \[ \log_4(64) = \log_4(4^3) = 3 \]
Putting it all together:
\[ \log_4(16 \cdot 64) = \log_4(16) + \log_4(64) = 2 + 3 = 5 \]
Thus, the answer in its simplest form is:
\[ \boxed{5} \]