Which of the following is a method used to calculate percentage changes?

The method used to calculate percentage changes is derived from the fundamental concept of comparing an increase or decrease in value relative to its original value, which is known as the old value. The formula takes the difference between the new value and the old value and then divides that difference by the old value.

This is expressed as (New - old) / old. In this formula, the "New" represents the updated value, while the "old" signifies the original or starting value. The result of this calculation provides the change in value as a fraction of the original value, and when multiplied by 100, it can be converted to a percentage. Thus, this method effectively measures how much a quantity has increased or decreased in relation to its original state, allowing for clear communication of the extent of the change.