Divide: $0.45$ by $9$.

Hint: In this problem, to find the required value first we will convert the given decimals into fraction. Then, we will simplify the obtained expression.

Complete step-by-step answer:
In this problem we have decimal $0.45$ and the whole number $9$. Let us convert the decimal into fraction. In the number $0.45$ we can see that there are two digits to the right of the decimal. So, this number could be converted into fraction by dividing $100$. So, we can write $0.45 = \dfrac{{45}}{{100}}$. Now the second number $9$ is the whole number. Now we have to divide the number $0.45$ by the number $9$. So, we can write
$0.45 \div 9 = \dfrac{{45}}{{100}} \div \dfrac{9}{1}$
Let us rewrite the above expression. So, we get $0.45 \div 9 = \dfrac{{45}}{{100}} \times \dfrac{1}{9}$.
Let us simplify the above expression. So, we get
$0.45 \div 9 = \dfrac{{45}}{9} \times \dfrac{1}{{100}}$
$ \Rightarrow 0.45 \div 9 = \dfrac{5}{{100}}$
$ \Rightarrow 0.45 \div 9 = 0.05$
Hence, the required answer is $0.05$.

Note: In fractions, the number above the line is called numerator and the number below the line is called denominator. For example, if the fraction is $\dfrac{{45}}{{100}}$ then $45$ is numerator and $100$ is denominator. The line which separates the numerator and the denominator represents the division. To convert the fraction $\dfrac{{45}}{{100}}$ into decimal, write the whole number $45$ with the decimal point $2$ spaces from the right because $100$ has $2$ zeros. That is, $\dfrac{{45}}{{100}} = 0.45$.