Is $+15/3$ a natural number? I know that $15/3=5$, and $5$ is a natural number, but is $15/3$ a natural number?
 A: Natural numbers are "one", "two", $\dots$. They are concepts. Usually one writes them as $1,2,\dots$. With respect to the set of rules stipulating what one can do with these numbers, we have 
$$
\frac{15}{3} = 5,
$$
say.
Hence $15/3$ is a natural number.
A: Yes. If you can equate it to a natural number, it is a natural number itself.
The equals sign "$=$" means that whatever is on the left side of it, is exactly the same as what is on the right side.
In the case of $$\frac{15}3 = 5$$ we have to recognize that whatever properties one side has, the other has also. So since 5 is a natural number, 15/3 must also be that, because they are equal to eachother.
A: Yes, precisely because $5 = 15 / 3$.
You should not mistake a representation of a number for the number itself. There are an infinite number of ways to represent the number $5$, but none of them changes the properties of the number $5$.
A: NATURAL NUMBERS are the subset of RATIONAL NUMBERS($\frac{p}{q}$).Therefore every natural number is rational number.
For x of the form $\frac{p}{q}$ where p,q $\in Z$.
If
 $x\in Q$ need not implies $x\in N$ .
but for some $x\in Q$ ,If x is positive and q=1,then x is a natural number I.e 15/3=5/1 is a natural number.
A: 
All natural numbers are rational numbers because they can be represented $p/q$ and where q=1 .
So , all rational number of form p/q ,where q=1 is natural number.

