How do you write 825 as decimal?

Divide 8 by 25 
Explanation: 
8 divided by 25 is dividing the numerator of the fraction ${\displaystyle \frac{8}{25}}$ by the denominator 25. 
${\displaystyle 8÷25=0.32}$ 
0.32 is ${\displaystyle \frac{8}{25}}$ in decimal form because fractions are converted into decimal form by dividing the numerator by the denominator.

Explanation: 
One method for converting a fraction to a decimal is to change the denominator to a power of 10, such as 10, 100, 1000, or 10,000.
For some fractions this is possible such as with denominators of: 2, 4, 5, 8, 10, 16, 20, 25, 40, 50, etc... Noticeably absent from this list are numbers which are prime numbers or multiples of 3, 7 etc. 
Top and bottom should be multiplied by the same number to obtain an equivalent fraction. This is equivalent to multiplying by 1, which has no effect on a number's value.
${\displaystyle \frac{8\times 4}{25\times 4}=\frac{32}{100}=0.32\Rightarrow (\frac{4}{4}=1)}$ 
If the denominator cannot be changed into a power of 10, then you have to divide the numerator by the denominator. 
${\displaystyle \frac{3}{7}=3÷7=0.4285714285\dots .}$ This is a recurring decimal. 
It can be shown as ${\displaystyle \overline{0.428571}}$ or rounded off to a suitable level of accuracy.${\displaystyle \frac{3}{7}\approx 0.429}$