00:01
We're given a half -life, and we're asked to use that to find an exponential decay function, and then the time when 77 % of an initial value remains, and the time when 6 .2 % of an initial value remains.
00:13
So we'll start by looking at our function.
00:16
We're given that the half -life, so t1 -half, is 5 ,730.
00:23
We know that the equation is the natural log of 2 over k.
00:27
And so if we set those equal, then we can solve for this k value, which we don't have.
00:34
So that's what we're looking for here.
00:36
So k will be 0 .0001.
00:43
And then, so this is carbon dating is the topic of this.
00:47
So we're going to use c of t.
00:49
So the carbon in terms of time is going to be the initial amount times e to the negative kt.
00:57
We're only asked about ratios.
00:59
Percentages or ratios of 77 over 100 and 6 .2 over 100, right? since we're only asked about ratios, our initial value isn't going to matter...