00:01
We define half -life as the amount of time it takes for half of the amount of the substance to decompose.
00:19
So that means say for example if you have an initial amount of 100 then after half -life it will go down to 250.
00:36
So in this case we're given with the table and we see here that from particularly if we see that from time 0 to time 30 so this is in sec this is in hours we find that the amount or the concentration of the substance in gram at time equals 0 to 20 at time equals 3 hours.
01:14
So as i corrected this should have been 3 not 30.
01:20
So as we see that as the amount has decreased by half it follows that time equals 3 is the half -life.
01:36
So we say 3 hours is the half -life.
01:44
So this is the first one we can establish from here.
01:49
Next we're going to approximate the amount remaining after 10 hours and 28 hours.
01:54
So we go ahead and check the table we continue writing it so we're actually given with time from 0 all the way to 18 and the intervals of 3 hours.
02:07
So 6, 9, 12, then 15 and then for the amount so we know that for every 3 hours there they have the amount decreases by half.
02:21
So we go from 40 to 20 and then from 10 to 5 and then to 2 .5 and then 1 .25.
02:30
We also have 18 there's 0 .63.
02:38
Now time equals 10 we have that right between 9 and 12...