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

Lesson 1: Basic addition and subtraction

# Basic subtraction

Introduction to subtraction. Created by Sal Khan.

## Want to join the conversation?

• where did the "-" sign come from? Who decided that meant subtract?
• I was wondering if it had any ancient roots, latin, egyptian, or something like that.

It looks like it does not. for a while, they used M and P, to mean minus and mer, (modern German mehr: more) and some people think that the "-" came from the tilde above the m, or could have just been short-hand for M.
• so we can understand that subtraction is the same as adding a negative number?
• Though, that only applies when you're adding a negative number to a positive number. If you're adding two negative numbers, then the result would be a positive sum rather than a negative one.
• Is 100 - 101 = -1 ?
• Yes. It would have to go into negative numbers. Who taught you that? That is above this level, but anyways, yes you are correct.
• To be honest i just wanna know..

who invented learning?
• Learning is something that predates the first humans. Monkeys are capable of learning to some degree.

Learning is a gift from nature.
• Who is the smartest person alive today?
• Who knows? There is no real, definitive way of knowing!
• How did we come up with the idea of subtraction?
• We can't tell for sure, but one possibility is the idea of losing something:

For example, you have some apples, I ate some of them, so you lost a quantity of apples. This is subtraction.

Can you think of more real life situations which we can represent using subtraction?
• Where did "-" sigh come from? Who decided that meant add
• The + sign originated from the Latin language where plus already meant: more
Greek language poly means: many
In writing it also means "also, and, & furthermore"

I hope this helped and hopefully even made sense