Radioactive decay is a first-order process and is described by this equation.
A = Ao e^(-kt) ……… where A is the activity at time t, Ao is the initial activity, k is the decay consant, and t is the elapsed time
The equation can also be written as …
ln A = -kt + ln Ao
The decay constant, k, is determined from the half-life.
k = ln 2 / t½ = 0.693 / 14.3 day = 0.0485 day⁻¹
A = Ao e^(-kt)
Ao = A / e^(-kt)
Ao = 30.3 / e^(-0.0485 x 2.00)
Ao = 33.4 g