SOLUTION: A radioactive sample with a mass of 80mg has a half life of 3 days. How long does it take for the sample to decay to 5mg? I got this far 5=80(1/2)^t/3 not sure what to d

Algebra ->  Exponential-and-logarithmic-functions -> SOLUTION: A radioactive sample with a mass of 80mg has a half life of 3 days. How long does it take for the sample to decay to 5mg? I got this far 5=80(1/2)^t/3 not sure what to d      Log On


   

Question 1167953: A radioactive sample with a mass of 80mg has a half life of 3 days.
How long does it take for the sample to decay to 5mg?

I got this far 5=80(1/2)^t/3
not sure what to do after this.

Answer by ikleyn(52802) About Me  (Show Source):
You can put this solution on YOUR website!
.

The mass ratio  current%2Finitial = 5%2F80 = 1%2F16 = 1%2F2%5E4.


Four half-periods:  3*4 = 12 days.

This problem is for easy MENTAL solution.