Question

What kind of rational number is 0?

Answer 1

What do you mean, exactly?

A number `\alpha` is said to be rational if there exist two integer numbers `n` and `m` such that `\alpha=\frac{m}{n}`. In particular, all integer numbers are rational numbers (which is what we mean when we say that `\mathbb{Z}\subset \mathbb{Q}`), because you can choose `m=\alpha` and `n=1`. And 0 is no different from all other integers: you can pick `m=0`, and for any `n \ne 0` you have that `\frac{m}{n}=\frac{0}{n}=0`, and so 0 is a rational number. If you can explain what you exactly meant with "what kind of rational", I'll be glad to answer:)