If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

### Course: Arithmetic (all content)>Unit 2

Lesson 1: Basic addition and subtraction

Let's learn about basic addition by starting with simple examples and moving on to more difficult problems. Two methods for solving these problems are demonstrated: drawing circles to represent each quantity, or using a number line. Practice is emphasized as the key to mastering this skill. Created by Sal Khan.

## Want to join the conversation?

• Why did you make your number line from left to right? Isn't it more intuitive to make a number line vertically? As you add numbers you move up the page, as you subtract numbers you move down the page. (Like an elevator, or a lego tower. as you add lego's onto your tower, the tower gets taller)
• Awesome question. You could use a vertical number line and when you get further in math you will use a combination of two or more number lines. The most logical explanation seems to be that the horizontal number line makes sense because that is how you read in some languages (such as English which is Sal's language ;-) ). Would be interesting to find out if people who use languages which are vertical use vertical number lines instead ...
• Is addition used when we grow up?
• Yes, for example, if you want to know how much money you have, you need to add it all to get the total
• Where did the word "addition" come from?
• "Addition" and "add" are English words derived from the Latin verb *"addere",* which is, in turn, a compound of "ad (to)" and "dare (to give)", from the Proto-Indo-European root deh₃- "to give"; thus to add is to give to. Using the gerundive suffix "-nd" results in "addend", "thing to be added". Likewise from "augere (to increase)", one gets "augend", "thing to be increased".
• Basic addition is "easy addition", with questions like 3+2=__ or 1+2=__
• So If I add 1 with 1 I get 2?
• Yep, you're right! 1 + 1 = 2.
Just picture a number line. If you start at 1 and go 1 hop to the right (you don't want to go to the left because that would be subtracting), you land on 2!
• How is arithmetic used in the real world?
• Everywhere, how do you think the internet works? Hamsters? No, arithmetic.
• When did people start using numbers?
• Roman numerals are coming from 500 BC, which is 2500 years ago
And usual numbers (arabic numerals) are coming from no later than V century which is minimum 1500 years ago
• Why do you guys think we should use addition, like, what's the purpose for using it? And why would ya think Sal said "Basic"? It totally makes sense doesn't it?
• Hey, how many years have passed since you posted this comment? Well, it was zero years when you posted and it has been a year since you posted it. So the math is 0 + 1 = 1 year