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Weird math question; Not particularly complex though
Topic Started: May 29 2013, 09:54 PM (547 Views)
Alancar
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I'm a magical princess from another dimension
How would you solve this:

8 - 2 + 1 = ?
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IH
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The Ever Curious
7

8+(-2+1) = 7

I believe.
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BlackFredric
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Oromë, Lord of Forests, the Great Rider, and Hunter of Valinor
8-2=6

6+1=7

Just a simpler version Intelligent Hologram's answer, which I also think is correct.
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Majestas
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Shelob
Actually, it does not matter the order you do it in.
8 - 2 + 1 = 8 + -2 + 1
Because of this, you can do it in any order, so it could be like so
8 + -2 + 1
8 + 1 + -2
1 + -2 + 8
1 + 8 + -2
-2 + 8 + 1
-2 + 1 + 8
Anyway you do it, it will be 7
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Jahmurai
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Azog Soulreaver
Well if 8 - 2+1 IS the problem to solve, then it is indeed 7.

But if you say 8 - (2+1) then it would be 8-2-1 which is 5
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Alancar
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I'm a magical princess from another dimension
Right. It's weird cause I just saw this video

Order of operations is wrong

I really like this guys videos but this was really weird. He says that there is this thing he calls order of operations that you supposedly learn in the US and most of the world, and according to it you are supposed to do addition first and subtraction latter.

In which case you would solve it like Jah suggested and get 5.

I did learn something akin to it in school, and it basically said you should do divisions and multiplication before addition and subtraction. But never addition before subtraction.

I was wondering if any of you would solve it like that.

Weird right?
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IH
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The Ever Curious
I saw that video as well, not one of his best, IMO.

In Britain we learn BIDMAS (brackets, indices, division, multiplication, addition, subtraction). I was always taught, though, that you treat negative numbers as their own number ('-2') as opposed to ('x-2') to give the value of the number.

Basically, I put an '+' in front of every number and treat the sum like this:
+8 + -2 + 1 --> +8 + -1 --> +8 - 1 = +7 or 7

I think the guy on the video is saying that if you follow the order of operations you will get 5 but the correct answer is actually 7.
Anyway , on every calculator I've used it gives the answer 7
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Charax
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Mordor's White Rapper Wizard
BODMAS

Brackets
Others
Division
Multiplication
Addition
Subtract

Addition comes before subtraction, therefore the problem is equivalent to:

8 - (2+1)
8 - 3
5
Edited by Charax, May 30 2013, 05:30 PM.
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Alancar
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I'm a magical princess from another dimension
huh...well I guess its a real thing then
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Charax
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Mordor's White Rapper Wizard
It's what they teach me in GCSE Maths.
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Majestas
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Shelob
We learn PEMDAS (parantheses, exponents, multiplication, divition, addtion, subtraction). However, one of the things was that M and D are at equal levels and it does not matter what order you do it is, as is A and S
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IH
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The Ever Curious
Yeah, it's the same with BIDMAS/BODMAS.

I believe in this situation the answer is actually 7.
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Majestas
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Shelob
And if you look at my first post, the addition and subtraction have to be at the same level because all subtraction can be turned into addition! Argo, the order of operations is right as long as you consider M and D to be interchangeable along with A and S
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Charax
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Mordor's White Rapper Wizard
A and S are not interchangeable. Addition always comes first.

IH, the answer is 5. You made the mistake of inputting a -2 when the correct digit is +2.
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IH
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The Ever Curious
Where does it say +2 and not -2?

The only answer Google gives is 7.
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Charax
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Mordor's White Rapper Wizard
Because Google is wrong. :P

Google assumes you mean negative two, when you actually mean subtract two.
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IH
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The Ever Curious
Google is never wrong.

I'm still going with 7.

5 is too easy for it to be right.
Edited by IH, May 30 2013, 10:26 PM.
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Charax
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Mordor's White Rapper Wizard
Two easy. Anyone?
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Alancar
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I'm a magical princess from another dimension
Charax, there is no doubt the answer is 7
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Wibblefeet
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Come with me if you want some Carrots
7. Addition and Subtraction are EQUAL IN PRIORITY, and performed left to right, in the absences of any parentheses or brackets or the like. Same for Division and Multiplication.
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