Question 1025723
the drug reduces by 28% each hour.


level of the drug after 1 hour is therefore 1 - .28 * 1 = .72


you want to find when the drug reaches .5


formula to use would be .5 = .72 ^ n


n equals the number of hours.


take the log of both sides of this equation to get log(.5) = log(.72^n).


since log(.72^n) is equal to n * log(.72), the equation becomes log(.5) = n * log(.72).


divide both sides of this equation by log(.72) to get n = log(.5) / log(.72).


this results in n = 2.110010956 hours.


since 2.11 hours is close to 2 hours, you would probably recommend the pill be taken every 2 hours.


in 2 hours, the level of the pill would be .72^2 = 51.84% of its original strength.


that's pretty close and much easier to remember than 2 hours and 6 or 7 minutes.