00:01
So we've got $450 ,000 to invest, and we've got an option of investing in something that returns 6 % or something that returns 10%.
00:11
So we're going to define x as the amount we invest invested in the 6 % category, and y is the amount invested in the 10 % return investment.
00:36
Those are return on investments.
00:42
And we've been specified, or it's been specified, that we have to invest at least in the 6 % investment, at least 250 % of the investment, or 225k.
00:56
So we can say x has to be greater than or equal to $225 ,000.
01:07
We want to have at least 50 % invested there.
01:10
And y has to be greater than or equal to 25%.
01:15
Or a quarter of the investment money, which is, again, we have a $450k total, so that would be $112k.
01:32
And we know that the amount we make from this is really going to be the profit or the amount return on the investment is going to be the amount we invest in 6 % times 1 .06, plus the amount we invest in, in the 10 % times 1 .1.
01:55
So the return on the investment, and we'll write this as roi, total is equal to 1 .06 times x plus 1 .1 times y.
02:16
And we know that the total x plus y can't be more than 450 because that's how much we have to invest.
02:27
So if this is our x -axis, this is our y -axis? we know that somewhere over here, say 225, we have to be, x has to be greater than 225.
02:48
So we have to be somewhere in this region.
02:53
X has to be greater than that value.
02:59
And we know also that y has to be greater than 112.
03:05
So we could draw a line there somewhere in here.
03:13
And y has to be greater than that.
03:21
So we're really talking about the intersection of those regions is somewhere in here.
03:26
But the other requirement we have is x plus y is equal to 450.
03:30
Well, what does that look like from an equation standpoint? we could write it in y equals mx plus b, something we're used to.
03:38
Y equals negative x plus 450.
03:45
So let's extend our y -axis a little bit here.
03:48
And let's imagine it looking something like that.
03:54
So that's basically a slope of negative 1 with a y intercept of 450.
04:03
450 there.
04:04
So that's pretty clear.
04:06
Y intercept.
04:08
But we also know this point down here is that when y equals 0, x is going to have to equal 450.
04:16
That's the x intercept right there.
04:22
So to figure out what the optimum investment is, we need to look at the intersection points of these three investments or these three extreme situations...