Answer:
y = 700 (0.969)^t
Step-by-step explanation:
Using the depreciation formula after a given period of time.
A = P (1- r/100)^n
Where, A is the initial value
P is the original value
r is the rate of depreciation and
n is the time taken in years
Therefore;
A will be the new mass of the sample after decay,y
P is the original mass of the sample before decay, 700 mg
r is the rate of decay each year, 3.1% and
n is the number of years, t
Hence;
y = 700 (1- 3.1/100)^t
y = 700 (96.9/100)^t
y = 100(0.969)^t