Question

Radon-222 is a radioactive gas with a half-life of 3.82 days. How long would it take for fifteen-sixteenths of a sample of radon-222 to decay?
15.28 days
30.56 days
45.84 days
49.66 days

Answer 1

\[\Huge t=\frac{\log\frac{A_E}{A_O}}{\log0.5} \times t_{\frac{1}{2}}\]
t is the time it would take
t1/2 is the half life
AO is the amount of substance at orignial time
AE is the amount of substanse left
\[\Huge t=\frac{\log\frac{\frac{1}{16}}{1}}{\log0.5} \times3.82days\]
\[\Huge t=15.28\]

Answer 2

Thank you, that's the formula I needed.