   SEARCH HOME Math Central Quandaries & Queries  Question from Aaron, a student: I understand how figure percent of change and I can figure it on a calculator but if I have to do it without I'm not sure how to divide when the original amount is larger than the amount of change. For example, the decreased amount is 5.00 on 29.99, what would the percent be. Like I said I can do it on a calculator but need to know how to figure it without one. Thank you.. Hi Aaron,

If a quantity changes from a starting value to a final value then the percentage change is

(final value - starting value)/(starting value) × 100

Thus if the starting value is 29.99 and the final value is 24.99 then the change is (final value - starting value) = -5.00 and the percentage change is

(final value - starting value)/(starting value) × 100 = -5.00/29.99 × 100 = -16.67%

We might also say that the quantity has decreased by 16.67%.

Penny     Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.