Adding and subtracting fractions leads to expected results: when you add two positive fractions, you get a larger number; when you subtract a positive fraction from something else, you get a smaller number.
However, multiplying by fractions between 0 and 1 yields unexpected results:
Multiplying a number by a fraction between 0 and 1 creates a product smaller than the original number. Note that this is also true when the original number is a fraction:
Conversely, dividing by a fraction between 0 and 1 yields a quotient, or result, that is larger than the original number:
This is also true when the original number is a fraction:
