To find a relative percentage decrease via a growth factor, you need to find the decay rate, by using the formula 

To find the relative percentage change via growth factor, you need to find the growth or decay rate, by using the formula y =a (1 ± r). This video explains. 

A decay factor helps you calculate a final amount after a percentage has been subtracted. It is given by the formula:

 is the decimal representation of the percentage that is being subtracted.

Indicates the percentage decrease between the initial and final amounts. Also known as decay rate.

The starting amount, before a percentage increase or decrease

The amount after you have included the percentage increase or decrease. It is given by the formula:

A measure of how much a quantity has changed expressed as percentage (%)

Growth Factors

How Do You Find a Percentage Decrease Using a Decay Factor?