Precision matters.
Finding the difference between decimal values.
Popularized by Simon Stevin in the 16th century to simplify interest calculations.
Line up the Dots! Give them ghost zeros.
In Plain English: It is exactly like regular subtraction, but you MUST line up the decimal points. If one number is shorter, fill the empty space with a zero.
In The Real World: Money. $20 - $14.50. You need to write 20.00 to make it work.
Subtracting from air. You can't do 'nothing minus 5'. You must write the placeholder zero.