How do you write $ 4.20 $ as a fraction?

Hint: We know that both decimals and fractions are used to represent the number that is not whole in two different ways. We use the decimal number to represent a non-whole number in which a decimal point is used followed by digits that represent a value that is smaller than one. Whereas, a fraction is a part of a whole number, a ratio between the upper number or the numerator and the lower number or the denominator.

Complete step-by-step answer:
Here, we are asked to convert $ 4.20 $ to fraction form.
We will convert it by following three simple steps.
In the first step, we will rewrite the decimal number $ 4.20 $ as a fraction where the decimal number $ 4.20 $ is numerator and the denominator is one.
 $ \Rightarrow \dfrac{{4.20}}{1} $
Now, we will multiply both the numerator and denominator by 100 as there are two decimal digits in $ 4.20 $ .
 $ \Rightarrow \dfrac{{4.20 \times 100}}{{1 \times 100}} = \dfrac{{420}}{{100}} $
Finally we will just simplify this fraction to its reduced form.
 $ \Rightarrow \dfrac{{420}}{{100}} = \dfrac{{42}}{{10}} = \dfrac{{21}}{5} $
Thus, our final answer is: $ 4.20 $ can be written in the fraction form as $ \dfrac{{21}}{5} $ .
So, the correct answer is “ $ \dfrac{{21}}{5} $ ”.

Note: Here, we are given the decimal term $ 4.20 $ which clearly seems to be greater than one. In the fraction for, the term is greater than one when the numerator is greater than the denominator. We can observe that in $ \dfrac{{21}}{5} $ , the numerator 21 is greater than the denominator 5. On the other hand, when the numerator is smaller than the denominator, we can say that the value of that fraction is less than one.