To determine the type of product that results from multiplying \( \frac{3}{5} \) and \( 3\pi \), we can analyze the elements involved:
- \( \frac{3}{5} \) is a fraction and also a rational number since it can be expressed as the ratio of two integers.
- \( 3\pi \) involves the mathematical constant \( \pi \), which is known to be an irrational number.
When multiplying a rational number (\( \frac{3}{5} \)) by an irrational number (\( 3\pi \)), the result is always an irrational number.
So, the answer is: an irrational number.