Answer:
231.59 years
Explanation:
To model this situation we are going to use the exponential decay function:
f(t)= a (1-b)^t
where f(t) is the final amount remaining after t years of decay
a is the final amount
b is the decay rate in decimal form
t is the time in years
For Substance A:
Since we have 300 grams of the substance, a=300. To convert the decay rate to decimal form, we are going to divide the rate by 100%:
r = 0.15/100 = 0.0015. Replacing the values in our function:
f(t) = a (1-b)^t
f(t) = 300 (1-0.0015)^t
f(t) = 300 (0.9985)^t equation (1)
For Substance B:
Since we have 500 grams of the substance, a= 500. To convert the decay rate to decimal form, we are going to divide the rate by 100%:
r=0.37/100= 0.0037. Replacing the values in our function:
f(t) = a (1-b)^t
f(t)= 500 (1-0.0037)^t
f(t)=500(0.9963)^t equation (2)
Since they are trying to determine how many years it will be before the substances have an equal mass M, we can replace f(t) with M in both equations:
M=300(0.9985)^t equation (1)
M=500(0.9963)^t 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, M, is :
{M=300(0.9985)^t
{M=500(0.9963)^t