Answer:
That equation is not typed correctly. Radioactivity decreases by what is known as exponential decay.
Pu 239 has a half-life of 24,100 years.
We need to calculate lambda which is natural log (2) / half-life
lambda = .693147 / 24,100 = 2.876 x 10^-5
Amount remaining = beginning amount • e ^ ( -λ • time )
Amount remaining = 100 * 2.718281828^(-2.876 x 10^-5 * 20,000)
Amount remaining = 100 * 2.718281828^-.5752
Amount remaining = 100 * 0.5625923391
Amount remaining after 20,000 years = 56.25923391 grams
Source: https://www.1728.org/halflif2.htm
Step-by-step explanation:
