Question

A radioactive substance decays exponentially. a scientist begins with 120 milligrams of a radioactive substance. after 14 hours, 60 mg of the substance remains. how many milligrams will remain after 19 hours?

Answer 1

First thing is you have to find the half life of the substance. The half life equation is
Final Mass = Initial Mass * 0.5^(time/time per half life)
Now we substitute the values given and we get
60 mg = 120 * 0.5^(14/t)
Solve for t and you get
t = 14 hours
Now plug 19 into the equation
Final Mass = 120 * 0.5^(19/14)
Final Mass = 46.84 mg