Subtracting a negative = adding a positive | Pre-Algebra | Khan Academy — Transcript

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1. 0:00This is Steve and this is Steve's uncle and Steve is in a bit of a bind.
2. 0:05Not only does he not have any money but he also owes Michael,
3. 0:09who is not depicted here.
4. 0:11He owes Michael $3. So he actually has a negative net worth.
5. 0:16Steve has a net worth of -3.
6. 0:18Steve's uncle cares about Steve and feels bad that he doesn't even have
7. 0:23a 0 net worth; he has a negative net worth!
8. 0:25And so Steve's uncle wants to at least take away some of this pain.
9. 0:29He at least wants to get Steve back to a neutral net worth, a 0 net worth.
10. 0:34So he decides to take away Steve's negative net worth.
11. 0:42He wants to take away that -3.
12. 0:45What happens if you take away that -3? Well, that should get you back to 0.
13. 0:51If you take away anything... if you have something
14. 0:54and you take it away, it should go back to 0.
15. 0:56Similarly if you owe people things and that owing people things
16. 1:01is taken away, it also gets back to 0.
17. 1:03And another way to think about it is how Steve's uncle would actually
18. 1:07take that liability, take that debt away from Steve.
19. 1:12Well, the easiest way he could do it if Steve is starting at -3 net worth
20. 1:16is for his uncle to give Steve $3, so that he(Steve) can get back
21. 1:22to a net worth of 0.
22. 1:24So hopefully, that makes it a little bit clearer,
23. 1:27that this and this are intuitively equivalent.