SOLUTION: Superman has been disabled by a nearby amount of Kryptonite. He cannot regain his power until 90% of the kryptonite disntegrates. If the half life of Kryptonite is 5 days, how l

Algebra ->  Exponential-and-logarithmic-functions -> SOLUTION: Superman has been disabled by a nearby amount of Kryptonite. He cannot regain his power until 90% of the kryptonite disntegrates. If the half life of Kryptonite is 5 days, how l      Log On


   



Question 379109: Superman has been disabled by a nearby amount of Kryptonite. He cannot regain his power until 90% of the kryptonite disntegrates. If the half life of Kryptonite is 5 days, how long will it be before he regains his powers?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
. He cannot regain his power until 90% of the kryptonite disntegrates.
If the half life of Kryptonite is 5 days, how long will it be before he regains his powers?
:
The remaining amt = .1
:
The half life equation
2^(-t/5) = .1
-t%2F5 = ln%28.1%29%2Fln%282%29
-t%2F5 = -3.3212
t = -5*-3.3212
t = 16.6 days
:
:
Check on a calc: enter 2^(-16.6/5}, results .100