Strategy #3: Percent Change Formula

For percent change always use (new − old) / old × 100.

Example: if the original price on a jacket is $145 and it is now on sale for $130, what is the percent change? In this case it’s the percent discounted.

(new − old) / old × 100

= (130 − 145) / 145 × 100

= −15 / 145 × 100

= −0.1034 × 100

= −10.34%

The negative sign indicates a decrease, so the jacket is discounted by 10.34%.