If the diameter of a mens basketball is 10 inches and a women’s is 9 inches, what is the appropriate difference of their volume

To model this situation we are going to use the exponential decay function: 
where
is the final amount remaining after  years of decay
is the initial amount
is the decay rate in decimal form 
is the time in years 

For substance A:
Since we have 300 grams of the substance, . To convert the decay rate to decimal form, we are going to divide the rate by 100%:
. Replacing the values in our function:


equation (1)

For substance B:
Since we have 500 grams of the substance, . To convert the decay rate to decimal form, we are going to divide the rate by 100%:
. Replacing the values in our function:


equation (2)

Since they are trying to determine how many years it will be before the substances have an equal mass, we can replace  with  in both equations:
equation (1)
equation (2) 

We can conclude that the system of equations that can be used to determine how long it will be before the substances have an equal mass, , is:


Solving the system, we can show that it will take approximately 231.59 years for that to happen.