Question 673868
 The radioactive element americium-241 has a half-life of 432 years.
 Suppose we start with a 20-g mass of americium-241.
How much will be left after 367 years? 
:
the radioactive decay formula: A = Ao*2^(-t/h), where:
A = resulting amt after t time
Ao = initial amt (t=0)
t = time of decay
h = half-life of substance
:
A = 20*2^(-367/432)
Use a calc
A = 20 * .5549628
A = 11.099 grams after 367 yrs