If digits follow a pattern that keeps changing (like increasing zeros or growing blocks), it is usually irrational because repetition never stabilizes.
Concept:
A decimal number is classified as:
• Terminating decimal $\rightarrow$ Rational number
• Non-terminating repeating decimal $\rightarrow$ Rational number
• Non-terminating non-repeating decimal $\rightarrow$ Irrational number
Step 1: Observe the pattern of the given decimal.
The number is:
\[
0.30300300030000\ldots
\]
We observe the pattern after decimal:
• 3 followed by 1 zero: 30
• 3 followed by 2 zeros: 300
• 3 followed by 3 zeros: 3000
• 3 followed by 4 zeros: 30000
The number of zeros keeps increasing.
Step 2: Check termination and repetition.
• The decimal is non-terminating.
• There is no fixed repeating block (pattern keeps changing length).
So it is neither terminating nor repeating.
Conclusion:
Since the decimal expansion is non-terminating and non-repeating, the number is:
\[
\boxed{\text{Irrational number}}
\]