00:01
We're given the number of tons of carbon emitted from the u .s.
00:04
And china, and then a growth rate per year for each country.
00:09
And we want to find how much carbon is emitted after 25 years for the u .s.
00:14
And for china.
00:15
And then we want to graph u of t and c of t for each country against each other to see what the differences are and what we can learn from that graph.
00:25
So we'll start by looking for the u .s.
00:28
We know it's 25 years because it started in 1995 and we want the year 2020.
00:37
That's how we got that 25.
00:39
We'll look at our equation.
00:41
U of t is equal to u0 our initial amount times e to the k t because this is exponential growth.
00:49
So we'll get 1 .4.
00:51
We know it's growing so we're going to do it in billions because the numbers will get bigger but not smaller.
00:56
So 1 .4 e to the k t we need this k value.
01:00
We know that in one year, u of 1 is equal to 1 .4e to the k times t is 1.
01:09
And we also know from a growth rate of 1 .3 % that there will be 101 .3 % the amount in one year.
01:17
So we can write that as 1 .03 times 1 .4.
01:22
And these will be equal to each other.
01:24
We can solve for our k value.
01:27
Our 1 .4 is we'll cancel.
01:29
We'll get e to the k is equal to 1 .013.
01:33
And that gives us that k is equal to the natural log of 1 .03.
01:40
And then we can plug this back into our equation.
01:42
U of t is equal to 1 .4 times e to the t times our k, natural log of 1 .013.
01:52
Now we have a t outside a natural log, so we can send that into the exponent.
01:56
And then we have e to a natural log in its exponent, and so those will cancel.
02:01
So we'll get, this is also equal to 1 .4 times 1 .013 to the t...