00:01
Okay, here we have decay and the formula for that is p equals a, p to the minus k, t.
00:14
Where a is a starting amount, p is the ending amount, t is time here in days.
00:25
So first step find the value of k.
00:29
Well, half life means half the material goes away.
00:32
So p becomes one half of a.
00:38
A .e minus k and t is five.
00:43
Five days.
00:45
So the a is cancel out and we end up with one half is equal to e to the minus 5k.
00:57
Then just take ln of both sides.
01:02
So we end up with ln of one half.
01:06
And the third law of logs the minus 5k goes in front times lne and lne is simply 1 which means we've now found k k will be ln of 1 half divided by negative 5...