Step 1: Identify the PDF.
The PDF is constant:
\[
f(x) = 0.01, 0 \le x \le 100.
\]
Step 2: Compute the mean of a uniform distribution.
A constant PDF over $[0,100]$ means $X$ is uniform on $[0,100]$.
Mean of uniform distribution is:
\[
E[X] = \frac{a + b}{2} = \frac{0 + 100}{2} = 50.
\]
Step 3: Final conclusion.
Thus, the mean is:
\[
\boxed{50}
\]