00:01
Hi there.
00:03
This question deals with half -life.
00:05
And half -life is simply defined as the amount of time it takes for half of a sample to decompose radioactively.
00:16
So in other words, if we talked about having a sample, say we have 100 % of it, and the first half -life passes, we would then only have 50 % of it remaining.
00:32
After the second half -life, half of that would decompose, and we'd have 25 % remaining, and so forth, for however many half -lives pass.
00:44
Each substance has a different amount of time for its half -life.
00:48
So in this problem, i am going to use the equation where nt refers to the amount remaining, and zero refers to the initial amount, and little n refers to the number of half lives that have passed.
01:16
In this question, it says that 75 % of it needs to decompose before this patient can leave the hospital.
01:25
Well, if 75 % disappears, that means the amount remaining is going to be 25 % for 0 .25...