00:01
So for number 70 in section 4 .4, we're looking at a country that has some coal reserves of 50 million tons.
00:11
And they give us two functions.
00:13
One represents the rate of consumption, how quickly in millions of tons per year that country is using the coal.
00:23
And then the second function they're giving us is the total coal in millions of tons used in t years.
00:31
So they're asking, when will the coal reserves be depleted? so when is this country going to use up the 50 million tons of coal? so there's two functions here.
00:46
That means one of them is probably a distractor, right? so if we're looking at millions of tons in our reserves, that would mean that we want to use the total coal function, because that's in millions of tons.
01:02
Those units agree.
01:05
So we're going to see when the coal used in t years is going to actually equal 50 million tons.
01:13
So we'll set that second equation, the t equation, equal to 50.
01:20
And we'll go ahead and we'll solve this algebraically...