00:01
Alright, so we have this company and they produce, they have two products, product a and product b.
00:05
Product a has to work on machine one for two hours and machine two for three hours.
00:12
Product b, it's one hour on machine one and four hours on machine two.
00:19
You can only use machine one a thousand hours for the day or the week or whatever and you can use machine two, it's only available for 2 ,500 hours during the week or month or whatever the time unit is.
00:32
Product a gives us a profit of $20 per unit, product b gives us a profit of $25 per unit.
00:40
Okay, so we want to maximize our profit.
00:46
Alright, so here we go.
00:50
How do we do this? alright, so machine one, right, if we look at machine one, we know that if we go to a, right, two times product a plus one times product b, we know that that has to be less than a thousand hours, less than or equal to 1 ,000 hours because that's all the time we have for machine one.
01:31
If we do the same thing for machine two, three times a plus four times b has to be less than or equal to 2 ,500 because that's how much we're limited by the hours of machine b.
01:55
So if we graph these, if you think of a little graph here, here's product, we'll call this one product a down here and this will be product b up here along the side.
02:13
So when we graph that first equation, two a plus b, if we don't make any product a and we use all b, we're going to be up here at 1 ,000.
02:27
If we don't make any product b and we only use product a, make product a, this will be here at 500.
02:39
So this is our first little kind of constraint line and we can be less than that.
02:47
We can be inside of that.
02:49
Okay, if we look at machine two, i'll graph this one in red so you can tell.
02:55
If we don't make any product a's and we only make product b, 2 ,500 divided by four is 625.
03:10
So that's about right here.
03:12
If we only make product a and no product b, 833 .333, that's like right here, that's like right there.
03:31
So that's this constraint and we'd shade inside.
03:38
So our shades overlap in this region right here.
03:43
So one of the coordinates of the boundaries, one of those coordinates, either this one here, zero, zero, it's not going to be zero, zero.
03:54
This one here that we don't know, 500 comma zero or zero comma 625.
04:02
One of those is going to maximize our profit.
04:05
It's probably going to be this guy right here, but we don't know what that one is.
04:10
But to find it, what you do is take the top equation.
04:14
I'm going to multiply by negative four.
04:17
So we have negative 8a minus 4b.
04:21
I'm going to just say equal to negative 4 ,000.
04:26
And then the other equation is 3a plus 4b equals 2 ,500.
04:35
And when we add straight down, the b's are going to disappear.
04:39
We have negative 5a equals negative 1 ,500.
04:45
And when we divide by five, a is going to be, what is that, 300 right there.
04:54
So this point is 300 comma...