Main content

### Course: 7th grade > Unit 3

Lesson 4: Subtracting negative numbers fluently# Subtracting a negative = adding a positive

Find out why subtracting a negative number is the same as adding the absolute value of that number. Created by Sal Khan.

## Want to join the conversation?

- I learned this trick and I think it will help you guys:

(Example)

-7 + 8 = 1

You see -7 plus 8 = 1. Even though it says plus, in this case, we can

subtract and keep the sign of the larger number. 8 is the larger number so we keep the sign of the larger number (positive) and we subtract 7 - 8 = 1. The answer is 1.(77 votes)- I really forgot how to subtract negative numbers. Can someone tell me how so I can remember. Thnx!(9 votes)

- Can we all just take a moment to appreciate Steve’s uncle for being so kind and caring to his nephew?(46 votes)
- How is adding a negative equivalent to a negative? How is it possible?(3 votes)
- Well, it depends on what the negative number is. For example, in 5+(-7), since the number 7 is greater than 5, you take away more than you have, so you then have a negative amount. 5+(-7) basically equals 5-7, which equals -2.

For example:

If you have $5 in your bank account and you spend $7, you have $0, but you also owe $2(42 votes)

- Let us all remember Steve's uncle for being so loving.(26 votes)
- can u explain it better for me please(2 votes)
- The two negatives cancel each other out, because negative negative would just be another positive.

On the other hand, a positive and a negative would equal a negative as the two signs aren't the same.

Ex.

2-2=2+(-2)

but

2-(-2)=4, not 0.

To help, think of it like -(- just being a disassembled +

They even look similar!

+ -(-(11 votes)

- Also,my teacher showed me a word problem for a warm up and it said that someone had -3 dollars. How can you have minus three dollars in cash?(3 votes)
- Think of this situation.

You have $5 dollars, but you want to buy something from your friend for $8 dollars.

5 - 8 = -3

You now owe your friend $3 before you start making any money for yourself.

You are now at -$3 dollars. You get $20 for your birthday. How much money do you have now? You have $17 because you have to pay your friend back the $3 dollars you owe them.

-3+20 = 17

Great question and hope this helps <|:)(10 votes)

- COMO QUESOOOO (translate that )(5 votes)
- How would we get this problem in the first place? Come on people everything has a reason.(4 votes)
- This example is totally understandable and clear. But if a negative number can also be minused from a positive number and that makes sense, then an example for that could also be added in the video to help further clear doubts.

If someone reads it, please give me a real life example of:

$2000 - (-$500)(2 votes)- The answer is $2,500 because the -(- turns into a plus sign.(4 votes)

- why am i doing this again?(3 votes)

## Video transcript

This is Steve and this is Steve's uncle
and Steve is in a bit of a bind. Not only does he not have any money
but he also owes Michael, who is not depicted here. He owes Michael $3. So he actually
has a negative net worth. Steve has a net worth of -3. Steve's uncle cares about Steve
and feels bad that he doesn't even have a 0 net worth;
he has a negative net worth! And so Steve's uncle wants to at least
take away some of this pain. He at least wants to get Steve back
to a neutral net worth, a 0 net worth. So he decides to take away
Steve's negative net worth. He wants to take away that -3. What happens if you take away that -3?
Well, that should get you back to 0. If you take away anything...
if you have something and you take it away,
it should go back to 0. Similarly if you owe people things
and that owing people things is taken away, it also gets back to 0. And another way to think about it is
how Steve's uncle would actually take that liability,
take that debt away from Steve. Well, the easiest way he could do it
if Steve is starting at -3 net worth is for his uncle to give Steve $3,
so that he(Steve) can get back to a net worth of 0. So hopefully, that makes it
a little bit clearer, that this and this
are intuitively equivalent.