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## Class 1

### Course: Class 1>Unit 2

Lesson 1: What is addition?

# Intro to addition

Learn what it means to add. The examples used are 1+1 and 2+3. Created by Sal Khan.

## Want to join the conversation?

• Where did the symbols for additional (+) and subtraction (-) come from?
(4 votes)
• The plus and minus signs (+ and −) are mathematical symbols used to represent the notions of positive and negative as well as the operations of addition and subtraction. Nicole Oresme's manuscripts from the 14th century show the earliest uses of the plus sign (+). The − may be derived from a tilde written over m when used to indicate subtraction, or it may come from a shorthand version of the letter m itself. The alphabet 'm' was used as the minus sign in the Europe until these symbols were intoduced
(26 votes)
• who actually made addition? like as in, who invented addition?
(141 votes)
• The process of addition was first thought of by the Chinese a long, long, long time ago!

They used something called an abacus to add things up, because the addition sign was not created until 1544.
(126 votes)
• Which one is easier subtraction or addition?
(6 votes)
• Personally addition but they are both farily easy.
(14 votes)
• how many numbers can you add at the same time?
(5 votes)
• You can add as many numbers at once as you want.
(11 votes)
• How would you add in different number bases?
(4 votes)
• (6 votes)
• How is addition like counting?
(5 votes)
• When counting you are adding by 1.
For example, when counting 1, 2, 3, 4, 5, etc., you can represent every number as an addition: 1, 1+1, 1+1+1, 1+1+1+1, 1+1+1+1+1, etc.
(2 votes)
• do you have a quick way too do 10+24+9+8+12+4+56
(3 votes)
• Yes, there are plenty of tricks.
1) In 10+24+9+8+12+4+56 find groups of ten(s) first. For example, add 4+56, and that will get you 60. If you are doing it on paper, you can cross out 4+56 and write "60" above it. Do that for other numbers, such as 8+12 = 20. when you do all of them, add the ones that do not make a group of 10 or more. Add those, to the groups of ten, and you got the answer.

2) Since this is addition, you can rearrange the numbers in an order that is easier to calculate, for example, 12+8+56+4+10+24+9.

3) Use a calculator (but sometimes thats cheating
(2 votes)
• If you add a negative and a positive, is it the same as subtraction?
(2 votes)
• Yes. Think of it like you have 3 dollars, but you are in debt of your mother for 2 dollars. You would be adding 3 to 2 dollars of debt, which is the same as 3-2. Hope this helped!
(5 votes)
• Can You Do Triple Addition Like 9 + 10 + 2 =21?
(2 votes)
• can you add double digits? like 22 + 33
(2 votes)
• Of course. It's very similar to how you add single digits. You just line the places up like the ones with the ones and the tens with the tens. Like this.
22
+33
_____

After you line it up, you just add down the columns, starting on the right. 2+3 for the right side, then2+3 for the left side. You will learn more about this later though. That was just a super quick example.
(2 votes)

## Video transcript

Voiceover:Let's think about what it means to add numbers. So let's start with 1. 1 plus. 1 plus 1. What is this going to be equal to? One way to think about this is we have 1 thing, and that thing will be a purple circle. So let me put that here. So that's this 1 thing. I'm just going to represent it with a purple circle. And I'm going to add another 1 thing. And since this is in blue, I'll make that other circle, I'll make that in blue as well. So let me put that right over here. So 1 plus 1. 1 plus 1. How many total circles do I now have? Well, I now have 2 circles. I now have 2 circles. 1 plus 1 is equal to, is equal to 2. Okay, you're saying all right Sal, all right, that makes sense. Let's do this with larger numbers. So let's say we want to know what equals ... And I'll put a question mark over here. So, question mark. What equals ... So something is equal to, is equal to, let's say, 2, 2, 2 plus 3. Something is equal to 2 plus 3. What is this something going to be? I encourage you to pause the video and think about it on your own. Well, you could view this as, I have 2 objects and then we're going to add another 3 objects. How many total objects would I have? So you have your 2 objects, which I'll use purple circles again. So let me ... Let me, so, we have 1 and 2 purple circles. This is the 2 right over here. And then to that we're going to add 3 more. 3 more circles. I'll represent those in blue because we wrote the 3, here, in blue. So that is 1, 2, and 3. So how many total circles do we now have? Well, we could count them. We have 1, 2, 3, 4, 5. In fact, let me count that. 1, 2, 3, 4, 5 circles. So 2 plus 3. 2 things plus another 3 things are 5 things. So our question mark, right over here, is equal to 5. So instead of writing the question mark right over here, let me clear that out. I could say 5 is equal to. I could write down that 5 is equal to 2 plus 3.