The increase from A to B is calculated as

(B - A)/A*100%

If B is smaller than A, the "increase" will be negative, indicating a decrease.

Example

Yesterday, the price of gas was $2.19 per gallon; today it is $2.25 per gallon. What is the percentage change?

(2.25 - 2.19)/(2.19)*100% = .06/2.19*100% = .0274*100% = 2.74%

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For A=0, the percentage change is undefined.

(B - A)/A*100%

If B is smaller than A, the "increase" will be negative, indicating a decrease.

Example

Yesterday, the price of gas was $2.19 per gallon; today it is $2.25 per gallon. What is the percentage change?

(2.25 - 2.19)/(2.19)*100% = .06/2.19*100% = .0274*100% = 2.74%

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For A=0, the percentage change is undefined.