What is rational inquire?

Yes, the product of two rational numbers is always a rational number.

Depends on where you are. In British (and Australian) English an enquiry is a general question, and inquiry is a formal investigation. So enquiries, general questions, inquiries, formal...

No. For example, 20.5 is irrational; indeed it was one of the first irrational numbers to be discovered.

The fact that they can be expressed as a ratio of two whole numbers (with the denominator being non-zero).

Unless you multiply 0 with some irrational number, it is impossible. Here's why: Let x,y be rational with x = a/b, z = c/d and y be the irrational number. If we presume xy = z then we have y = z/x....