 Let me ask you this. What's the ultimate purpose of mathematics? Basically, math was developed to help us answer questions, okay? To help us solve problems, to help us explain systems, to help us understand life and optimize our ability to interact with it, okay? There is no other language that we've been able to come up with, okay? That does this better than mathematics. Now, the first place, the first place where we start using math in life, in our everyday life, and in trying to understand how things work, is by introducing units to numbers. And what units do in mathematics is they give meaning to numbers, okay? Take for example, the number two. Any number, number two. That's just a number, right? There is no meaning behind that. That's just a number. It's just the number two. It's the same thing as this other two, right? This two and this two are the same two. I can put an orange two. Two, two, two. They all mean the same thing, right? As soon as we introduce units, two numbers, these numbers begin to mean something, right? Two apples. Two people. Two oranges. And you can continue with this, right? Two kilometers, two miles, two kilograms, two triangles, two points, two anything you want, right? As soon as you introduce units, two numbers, you give numbers meaning. And as soon as you do that, you can start using them in your life, in any system that you're trying to understand, in any system you're trying to explain, right? In any system that you're trying to optimize, right? That's what units do. Some units, they're just there. They're part of our everyday lives. Two apples, two people, two oranges, two sheep, right? They're there. It's something we can understand, right? Certain units we created to be able to dig down deeper into whatever system that we're trying to understand, right? If we're trying to weigh something, we came up with two kilograms, right? If we're trying to measure something, we came up with two kilometers, two miles, right? And all these systems didn't come out like this. There were other systems all over the world that existed that didn't mesh together, right? They didn't work together. You have to convert from one system to another system for you to understand it. Currency is one, right? One dollar in the United States is different than one dollar in Canada. It's different than one dollar in Australia, right? Take the euro, for example. All the separate countries in Europe that now belong to the European Union that use the euro, the same currency, they all have their own different currencies. So if you travel from one country to another, you have to do a conversion. You have to figure out how much your money was worth in the other country, right? So what they did was harmonize that and create one system. And that's the way most of the systems, most of the units that we're going to use, that we've come up with that we use in our everyday lives either to make things, to measure things, to do commerce, to cook, to bake, to do everything in our lives that requires a certain amount of mathematics and almost everything in our lives does require a certain amount of mathematics. All of those systems, most of those systems that we use in mathematics to a certain degree, we've come up with as convention, right? And slowly throughout the ages, we've been able to harmonize some of those systems. So units are either something that existed that we're able to, you know, just throw in after a number, understand what that means. You know, two apples. I have ten sheep. You know, there are two people here. There are five people here. There are a thousand people here. Or there are units that we came up with to be able to understand the system, to be able to explain the system, to be able to dig down into a system and to be able to do predictions and to be able to work with them. Okay? And that is the main problem that most people face when they start doing unit conversions, when they start entering into the realm of chemistry, biology, economics, whatever system you want to enter, music, poetry, literature, right? Everything has a unit associated with it. Everything is based on a system that you have to understand before you can start using it, okay? Keep that in mind because that's all units are. And that's one major obstacle that people face that I know I face that there are times when I encountered certain types of units where even though my mathematics was strong, I just didn't have the ability to apply that. I had a really hard time applying that, you know, learning that system and doing well in whatever it was that I was taking, either if it was chemistry, biology, if it was music, music theory, whatever system it was, I stumbled, right? Until I learned what the units meant, until I learned all the different types of units that existed in that system to be able to convert from one to the other. And then I started doing better in whatever it was that I was doing better in, okay? So just keep that in mind. All units are is, units give meaning to numbers and once you start giving meanings to numbers, you can start using those numbers, you can start using the axioms we've come up with, the rules of mathematics in that system, in real life, in whatever it is that you're trying to do. Crazy view. Now your prerequisite for this stuff is some of the beginning sections in series one, which is basically section one, section two, section three, you know, learning how to deal with fractions, learning how to crunch numbers, learning how to, you know, what prime numbers are, learning the real number set, okay? You're going to have to learn how to move around an equal sign because that's where we're going into, right? Equal sign is sort of beginning stages of using mathematics in real life, as soon as you give them units, right? As soon as you give numbers units and start using the equal sign, now you're looking at a specific system trying to figure out if one side of an equation equals another side of an equation specifically based on your units you're talking about, based on the system that you're talking about, right? Based on the system that you're exploring, okay? So there's some prerequisites you need, which is basically learning how to do simple arithmetic for us, for you to be able to understand what we're going to do in this section. This, you know, in association with ratios, because ratios is, you know, one major aspect of this, which they're basically connected, especially when you're doing converting from one unit to another, okay? That's what units is going to be. It will be interesting and we'll try to touch on a few different subjects. And some of the initial stuff we're going to start off with should be quite fun and still apply in, if not your everyday life in your life at some point or it could apply in your life at some point, okay? We'll talk later. See you guys in the next video. Bye for now.