The amount left after 20 years = 154.15 mg
<h3>Further explanation
</h3>
The atomic nucleus can experience decay into 2 particles or more due to the instability of its atomic nucleus.
Usually radioactive elements have an unstable atomic nucleus.
The main particles are emitted by radioactive elements so that they generally decay are alpha (α), beta (β) and gamma (γ) particles
The decay formula for isotope :

Then for t=20 years, the amount left :

Answer:
graduated cylinder
Explanation:
It shows exact volume very precisely.
I believe the correct answer is the second option. The type of decay that characterizes the change of nuclides to their respective daughter products would be exponential decay. This type of decay is characterized by the decrease of quantity of a material according to the equation y=ab^x.