SOLUTION: A person drinks alcohol at a party. After her last drink, the alcohol level of her blood soon reaches a maximum of 0.28 milligrams alcohol per milliliter of blood. If the half li

Algebra ->  Logarithm Solvers, Trainers and Word Problems -> SOLUTION: A person drinks alcohol at a party. After her last drink, the alcohol level of her blood soon reaches a maximum of 0.28 milligrams alcohol per milliliter of blood. If the half li      Log On


   

Question 859111: A person drinks alcohol at a party. After her last drink, the alcohol level of her blood soon reaches a maximum of 0.28 milligrams alcohol per milliliter of blood. If the half life of alcohol in her blood is 2 hours, how long must she wait before driving at the legal limit of 0.08 milligrams alcohol per milliliter of blood?
All I know is that I have to divide something in half, but I don't know what or how to set up the equation. I think that I would use this equation but I am not sure A=A_0e^rt ? But I am not sure.
Thanks in advance for the help.
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Half life usually denotes using an equation with (1/2) as the base.
A=A%5B0%5D%2A%281%2F2%29%5E%28kt%29
where
A%5B0%5D%2F2=A%5B0%5D%2A%281%2F2%29%5E%282k%29
1%2F2=%281%2F2%29%5E%282k%29
so then 2k=1
k=1%2F2
so,
A=A%5B0%5D%2A%281%2F2%29%5E%28t%2F2%29