Question

Iodine-123 is a radioactive substance used in medicine. It has a half-life of 13 hours. A nurse received a solution that initially contained 48 grams of iodine-123. Now only 12 grams of the iodine-123 remain. How many hours have passed since the nurse received the solution?

Answer 1

Ok

A=P(1/2)^(t/h)
A=amount final
P=initial amount
t=time elapsed
h=time of half life

so

given h=13
and initial =48g
and final is 12g


12=48(1/2)^(t/13)
divide both sides by 48
1/4=(1/2)^(t/13)
what a coincidence
(1/2)^2=(1/2)^(t/13)
so
2=t/13
26=t

26 hours have passed