In computing percentages, what is the formula for percent change from A to B?

In computing percentages, what is the formula for percent change from A to B?

• A. Percent change = [(A - B) / B] × 100%
• B. Percent change = [(B - A) / B] × 100%
• C. Percent change = [(B - A) / A] × 100%
• D. Percent change = [(A - B) / A] × 100%

Answer: (C)

Percent change from A to B shows how much B differs from A relative to the starting value. The best formula is the change (B − A) divided by the original amount A, then multiplied by 100: [(B − A) / A] × 100%. This captures exactly how big the change is in relation to what you started with. For example, moving from A = 40 to B = 60 increases by 20, and 20 divided by 40 is 0.5, which is a 50% increase. If B is smaller than A, the result is negative, indicating a decrease. Using the final value as the base would answer a different question—what percent of the final value the change represents—so it doesn't measure the change relative to the starting point. Using (A − B)/A would yield the same magnitude but with the opposite sign, giving a misleading sense of direction.

Percent change from A to B shows how much B differs from A relative to the starting value. The best formula is the change (B − A) divided by the original amount A, then multiplied by 100: [(B − A) / A] × 100%. This captures exactly how big the change is in relation to what you started with. For example, moving from A = 40 to B = 60 increases by 20, and 20 divided by 40 is 0.5, which is a 50% increase. If B is smaller than A, the result is negative, indicating a decrease.

Using the final value as the base would answer a different question—what percent of the final value the change represents—so it doesn't measure the change relative to the starting point. Using (A − B)/A would yield the same magnitude but with the opposite sign, giving a misleading sense of direction.