Hello. I’m Professor Von Schmohawk

and welcome to Why U. In the first lecture, we explored

the origins of the first number systems. We also saw how the people

on my primitive island of Cocoloco first learned about the decimal number system. Once the Cocoloconians

discovered decimal numbers we could do much more than count coconuts. We could do arithmetic calculations with coconuts! The first arithmetic operations we invented

were addition and subtraction which came in very handy

when dealing with coconuts. For instance, if you have three coconuts and then your neighbor gives you five more you will have eight coconuts. Interestingly, if you start out with

five coconuts and then your neighbor gives you three more you will also have eight coconuts. For some reason, five plus three

gives you the same answer as three plus five. Eventually we figured out that it doesn’t matter in which order

you acquire your coconuts. You still end up with the same number of coconuts. Since the two numbers

on either side of the addition symbol can switch positions

without changing the answer we say that they “commute”

since commute means to travel back and forth. Mathematical operations in which

the numbers operated on can be switched without affecting the result

are said to be “commutative”. This illustrates what the Cocoloconians call The Commutative Property of Addition of Coconuts. Apparently, this property applies

to adding anything so we will just call it

The Commutative Property of Addition. So addition is a commutative operation. Instead of talking about specific numbers

like three and five if we call these two quantities A and B then we can write this property

in a more general way. Although addition is a commutative operation,

subtraction is not. For example, four minus three is one. However, if you switch the order of the three

and the four, the result will not be the same. Three minus four is negative one. As we saw in the previous lecture we can write four minus three as an

addition of positive four plus negative three. Now, since addition is commutative we can switch the four and the negative three

without changing the result. This is a trick which can come in handy

in algebra problems. Addition is a “binary operation”. Binary operations are mathematical calculations

which involve two numbers. These numbers are called “operands”

and in the case of addition these operands are added together

to produce a result called the “sum”. In addition operations, the operands are sometimes

referred to as the “addends”. Even though addition is defined as

a binary operation you may often see additions

involving more than two operands. This is possible because pairs of operands

can be added one at a time with each sum replacing the pair. In this way, an unlimited number of operands

can be added sequentially. The commutative property can be applied

to addition operations involving more than two numbers. By switching adjacent pairs of numbers,

operands can be reordered in any way we please. For instance, in this addition

involving four operands the two at the end

could be moved up to the front. Or the five could be moved to the back. In addition to the commutative property here is another interesting property of addition

that we discovered. Let’s say that you have five coconuts and your neighbor on the left has three. Both of you get together and pool your coconuts

into one group of eight. Then your neighbor on the right

gives you four more. Now you will have your group of eight

plus four more, for a total of twelve coconuts. On the other hand, let’s say you started out by pooling your five coconuts with your neighbor

on the right who had four coconuts. So you start out with a group of nine coconuts. Then your neighbor on the left

gives you his three so you end up with three

plus your group of nine or a total of twelve coconuts. You still end up with the same number of coconuts. In these two scenarios the coconuts were grouped

in different ways before they were added. However, we ended up with the same number. This illustrates what is called

The Associative Property of Addition because it doesn’t matter in which way

the coconuts are grouped or associated with each other

before they are added. In the end, they all add up to the same number. If we call these quantities A, B, and C then we can write this property

in a more general way. The commutative property of addition involves

moving around the numbers to be added whereas the associative property of addition

involves grouping them differently. Using the associative and commutative properties,

we can rearrange groups of numbers. Let’s see what this looks like

on a number line. As an example, we will take an addition problem

involving positive and negative numbers. Let’s start at the origin

and add positive two plus positive three plus negative six plus negative two plus positive four. This all totals up to one. However, because of the commutative property we are free to rearrange this sequence of

numbers in any order we like. For instance, we could add all the

negative numbers first and we will still get the same result. We could also use the associative property

to group some of the numbers to be added. For instance, the negative two

and the positive two could be grouped. Since this group adds up to zero,

we could replace it with a zero or eliminate it altogether. Having a familiarity with the

properties of addition allows us to start building a tool chest

of mathematical tricks which we can use later

to simplify complicated problems. In the next few lectures, we will explore

the properties of more arithmetic operations such as multiplication and division.

## 49 Comments

## Leo Gir

nice coat and pipe

## Leo Gir

coconut math algebra

## Clarisse Juco

thats good…………..

## yoomi

this amuses me

## savannah

Hilarious

## savannah

Nice pipe

## Sergio Santos Rosell

I will use the video for my bilingual class of maths. Thanx

## zeina ali

A look behind the fundamental properties of the most basic arithmetic operation, addition.

## Andrea Melendez

Thank you soo much I finally get it!

## LadyLove

Thanks this will be great to show my kids.

## Max the Big Bad

vids are so addicting it's like two AM

## MusIsWorld

Who would have thought the most basic and simple rules of math can be so entertaining 🙂

## Yusun Beck

These videos are awesome!!!

## Joubert Duvenhage

this is so cool !

## Sathya priyan

Awesome…

## Natasha Wheatley

So helpful thank you

## Carli Aldape

Very helpful!!!! Thank you!

## martin jimenez

This helped a lot thanks

## Adeline Kong

Thanks

## Ad Ship

This was so incredibly helpful! My girl did not understand these concepts until she watched this video. Please keep making them because they are SUPERB!

## Jana Malki

Thank you !! This helped loads with my homework.

## Its. Ric0

good job

## DiamondGirls116

I'm doing this for school:-(

## DiamondGirls116

Thx for the help though!:o3

## Raw Kay

Amazinggggg! Thaank youu

## Bria Eldon

Blah, blah, blah

## suliman babar

Thnx Sir for such an easy & helpful presentation.

## Susan Franco

Awesome! The 5th grade girls couldn't stop giggling about the coconut bras and they all learned the associative property! Thanks for the high quality lesson!!

## andrew kim

Cool!

## Gelica Armand

I LIKE IT

## Freddie Frillman

I love his "primitive island of Cocoloco". It stinks that they stop using it later on.

## Marion Bageant

Wish you could do one for second graders! I teach them number strings–commutative and associative property.

## Kevin Bires

thanks

## Swaralaya Studios

I love your video series.

## TonyTheActor

helps so much!

## Douglas

lol I love these

## dekippiesip

I like how this generalizes to group theory. You actually thought group theory to children without noticing it, but then applied on familiar numbers. But all terms here can be used when talking about matrices or other stuff!

## kgferg50

Oh, professor! A slip of the tongue! So near to perfect yet human after all – thank goodness! Only one letter in one word in the 83 videos I have downloaded – incredible! Check it out at 6:33. What a brilliant series – I look forward to many more episodes in the decades to come. Thank you, thank you, thank you!

## James Jr

so amazing and helpful!

## Khalil Raki

Reminds me of the Kingdom of Mocha.

## Lux Aeterna

Why the fuck wasn't this taught like this in middle/high school? I got some garbled "process oriented" memorize this crap instead of actual theory.

## Phoenix is Awesome

Coconuts

## Zachary Wormwood

He maintains that base ten number systems were "discovered." Mathematics is a social construction, base ten number systems and mathematics as a whole are not discovered, they are culturally agreed upon what some philosophers would call an artifact. Overall though, I will use this video to supplement my math class, thanks MuMathU.

## Victor

Do one with multipication

## Umais Shahid

What a beautiful work. Thank you very much sir.

## Keith Rogers

This is a perfect video, like how it ties together at end!

## 피이이이이이아아앙tv

this is good and right video!!!!!!!!!!!!!!

## G Honda

I can follow this…a miracle has occurred.

## Owen Garry

cooooocoooonuuuuts