SOLUTION: I would really appreciate some help with this one. The half life of a radio active substance is 125 days. How many days will it take for 82% of the substance to decay?

Algebra ->  Customizable Word Problem Solvers  -> Misc -> SOLUTION: I would really appreciate some help with this one. The half life of a radio active substance is 125 days. How many days will it take for 82% of the substance to decay?       Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


    

Question 402769: I would really appreciate some help with this one.
The half life of a radio active substance is 125 days. How many days will it take for 82% of the substance to decay?

Answer by scott8148(6628) About Me  (Show Source):
You can put this solution on YOUR website!
At = Ao (1/2)^(t/h) ___ At is amount at time t ; Ao is initial amount ; t is the time ; h is the half life

At / Ao = (1/2)^(t/h)

1 - .82 = (1/2)^(t/125)

log(.18) = (t/125)log(1/2)

[log(.18)] / [log(1/2)] = t / 125