How do you write the simple fraction equivalent to 0.9?

Hint: In this particular problem, we are given a decimal number. We have to convert this number into a fraction. Fraction consists of numerator and denominator. When we remove the decimal, the zeros will be added in the denominator followed by 1. These types of conversions are the easiest one.

Complete step by step answer:
Let’s discuss the given question in detail.
We already know that decimals are those numbers which represent the fractional part of a number. For example in 2.16, 2 is a whole number and 16 is a fractional part. The whole number and the fractional part are separated by the dot(.) symbol. When we remove the decimal, zeros will be added to the denominator followed by 1. The total numbers which are placed after the decimal will be counted so that we can place only that much zeros. If we remove decimal of 2.16 we will get 100 as a denominator like this: $\dfrac{216}{100}$ because after decimal there are 2 digits i.e. 1 and 6 so we will place 2 zeros after 1 in denominator. After this conversion, when we obtain a fraction, it can also be reduced to lowest terms.
We have:
$\Rightarrow $0.9
After removing decimal:
$\Rightarrow\dfrac{09}{10}$
There is only one digit after the decimal, so we have placed one zero in the denominator. So the required fraction is:
$\Rightarrow \dfrac{9}{10}$

Note:
Students usually get confused while removing decimal. They put the zeros in the denominator but forget to remove the decimal like this: $\dfrac{0.9}{10}$. No marks will be assigned after such a mistake. Secondly, do take care if the fraction is getting reduced into simplest form. If it is not getting reduced, leave as it is.