How do you write $2\dfrac{{51}}{{100}}$ as a decimal number?

Hint: In order to obtain the decimal equivalent of the above mixed fraction , first convert this fraction into a regular fraction of the form $\dfrac{p}{q}$ by using the rule $a\dfrac{x}{y} = \dfrac{{ay + x}}{y}$.Since the denominator in our case is already in the form of 10 raised to power some $n$, simply shift the decimal point of the numerator value towards left up to places equal to the exponent value of 10 or simply divide the fraction .

Complete step-by-step solution:
We are given a mixed fraction $2\dfrac{{51}}{{100}}$.
In order to write the decimal equivalent of the above mixed lets first convert this mixed fraction in the regular fraction of the form $\dfrac{p}{q}$by using the rule $a\dfrac{x}{y} = \dfrac{{ay + x}}{y}$
In our case we have $x = 51,a = 2\,and\,y = 100$
$2\dfrac{{51}}{{100}} = \dfrac{{2\left( {100} \right) + 51}}{{100}} = \dfrac{{200 + 51}}{{100}} = \dfrac{{251}}{{100}}$
To convert any fraction into a decimal number, we try to make the denominator in the form of 10 raised to the power some $n$. But in our case, there is no need.
$
   = \dfrac{{251}}{{100}} \\
   = \dfrac{{251}}{{{{10}^2}}} \\
 $
Now shift the decimal point of the numerator up to places equal tox the exponent value of $10$ i.e. 2 towards left side
$ = 2.51$
Therefore, the decimal equivalent of the fraction $2\dfrac{{51}}{{100}}$is equal to$2.51$

Note:
1. Cross-cross your result at least once.
2. To calculate fraction from the percentage , divide the given percentage value by 100
For example : We have to write $70\% $into fraction
$
   = \dfrac{{70}}{{100}} \\
   = \dfrac{7}{{10}} \\
 $
Or
$ = 0.7$
3. If the denominator of the fraction is not possible to make in the form of 10 raised to the power some $n$, then simply divide the fraction by long division to obtain the result.