Explain why it makes sense for the original amount to be the denominator when you write a proportion to find a percent change

Explanation:

Percentage change is about comparing the old values to the new values.

Let us consider first how do we calculate percentage.

Percentage =

Where the amount is something out of total.

When we talk about percentage change, we compare how the new value has changed compared to the old value. So for an instance if in the last season, a team won 10 matches out of 20, its winning percentage was 50%.

But in the new season the same team won 15 matches out of 24, the winning percentage is 62.5%. Here we can observe the difficulty in comparing the win percentage since two denominators are different, had it been same, it would have been easier for us to compare.

Writing the original amount in the denominator helps us compare the percentage better. It gives us a better idea of comparing the change, if we change the denominator, our frame of reference or the base of comparison will change and that cannot tell give us a fair comparison.

Therefore, the original amount is kept in the denominator while calculating the percentage change.