Final answer:
The subtraction of the fractions 1/3 - 7/21 resulting in 0 does not indicate that the fractions are proportional. Proportionality involves the equivalence of two ratios or fractions, not the result of subtraction.
Step-by-step explanation:
When looking at the expression 1/3 - 7/21, we can see that it represents a subtraction of two fractions. To understand if the result is proportional, we first need to make sure the denominators are the same. Since 21 is a multiple of 3, we can express 1/3 as 7/21. Now, the expression becomes 7/21 - 7/21, which simplifies to 0. This does not mean the fractions are proportional, though; it just means their difference is zero.
Proportionality in mathematics refers to the equivalence of two ratios or fractions. For example, the fractions 1/2 and 2/4 are proportional because they are equivalent; the simplification of 2/4 is 1/2. However, in the case of 1/3 and 7/21, although the modified fractions have the same denominator and their difference equals 0, it does not establish that the two fractions are proportional. They are simply equal to each other after the subtraction operation is performed.
To form a proportion, you would set two ratios equal to each other. However, having a difference of 0 does not reflect the relationship of proportionality; it just indicates equality or that one value has been subtracted from another to result in zero. This applies similarly to unit rates and unit scales, showing proportionality in different contexts.