# Only for Albert Einstein: 3-3×6+2=??

• Shows once again how broken the US Education system is and how idiotic the acronym "PEMDAS" is.

• how idiotic the acronym "PEMDAS" is.

I don't understand. Is the answer not -13?
Edit: nevermind, not literal enough I guess.

• Edit: nevermind, not literal enough I guess.

-13 is the right answer, and +2 is not horribly off (since some people reject PEMDAS). But both 17 and -17 are truly awfully wrong.

• Have i recently complained about how shitty disco is at displaying imgur albums? I didn't realise there were more images, until i hovered over it and hover-zoom came on.

Is the answer not -13?

How do you/they get there ? I cant even follow the logic there.

• #3-3*6+2

[poll]

• ((3-3)*6)+2 = 2
• (3-3)*(6+2) = 0
• (3-(3*6))+2 = -13
• 3-((3*6)+2) = -17
• 3-(3*(6+2)) = -21
[/poll]

I think that's all permutations.

• you missed fucking up and getting:

17

the logic presumably being ((3x6)+2)-3

• I got [2, -3].

Let's see if anyone can figure how

• cross product ? A while since i played with matrices..

• Either i'm way sicker than i thought (litteraly) or i'm getting old. I honestly thought it was -17, reason being plus and minus having equal precedence.

• reason being plus and minus having equal precedence

That's exactly why it's -13. Have you tried turning your logic on and off again?

As a computer scientist, you should know that equal precedence means the operations are evaluated from left to right.

• None of these posts are funny.

• That depends on the associativity.

• Either it is associative in which case it the order of evaluation doesn't matter (and you'll still go from left to right because who switches algorithms on a whim?) or it does matter in which case you go from left to right.

• No sane language would ever make the plus operator right-associative. Some languages are very creative with other operators, though.

• you should know

That's what scares me. And i thought i knew ...

• None of these posts are funny.

Well at least this is the right thread for them, then.

• #3-3*6+23 3 6 * - 2 +

RPNTFY
No ambiguity whatsoever.

• li fu'a ci boi ci boi xa pi'i vu'u re su'i

Yes, lojban supports reverse polish notation.

• PPMDSR on Spanish sounds awfully wrong.

• /me does the math carefully, in the process consuming about three reams of paper for her notes.

huh..... that can't be right.

according to my calculations the answer is "a potato"

• Odd. Did you check for @accalia's in your notes?

• according to my calculations the answer is "a potato"

Fried or mashed or what?

• Based on my calculations, 'dauphinoise'

• how broken the US education system is

FWIW, when pictures like that pop up in the Polish part of the Internet, the rampant idiocy isn't very different.

• Either i'm way sicker than i thought (litteraly) or i'm getting old. I honestly thought it was -17, reason being plus and minus having equal precedence.

My favorite is the one who taught math for 32 years. Do they not know that subtraction and addition are the same? That if you want to evaltuate the addition in that equation first, you need to keep the negative sign with the 18? Essentially: `3 + (-18 + 2)`.

• I suppose that most people just purge some things after they pass the test.

Of course I'd get a lot of calc wrong if I had to answer off the top of my head

• No sane language would ever make the plus operator right-associative. Some languages are very creative with other operators, though.

In APL, all operators are right-associative (or more accurately, all expressions are evaluated from right to left).

But even in algebra, before there was programming for real people, exponentiation has always been right-associative:

2^3^2 = 512
(assuming left-associativity would give you 64).

• APL

I said sane language.

• I said sane language.

What do you mean? It's a very sane language. Just arcane.

• Ok, to be fair, I've never looked into it.

• Well here's a sample of APL for you:

(2=+⌿0=(⍳ X)∘.| ⍳ X)/ ⍳ X←100

That produces all the primes 100 and below. It all makes sense now, right?

Stole-dit from APL Wiki

• Well here's a sample of APL for you:

(2=+⌿0=(⍳ X)∘.| ⍳ X)/ ⍳ X←100

That produces all the primes 100 and below. It all makes sense now, right?

Yeah, I know what it looks like. And judging from that, they should have named it WTP.

• I think that's all permutations.

Only if you assume Decimal and not Octal or Hex or ....

• Well here's a sample of APL for you:

(2=+⌿0=(⍳ X)∘.| ⍳ X)/ ⍳ X←100

That produces all the primes 100 and below. It all makes sense now, right?

I miss my MCM-800....

• Addition and multiplication are associative, subtraction and division are not.

Which is why you have to convert subtraction to addition or division to multiplication before you can reorder them.

• As a computer scientist, you should know that equal precedence means the operations are evaluated from left to right.

As an APL programmer, I reject your bizarre assertion.

• Just to close the circle, in APL 3 - 3 × 6 + 2 yields the result -21 (not -21, which is not a literal but an expression that happens to have the same value).

• I had to go back to primary school maths to get it.

This is what's taught in Irish schools

I am TR it took me two minutes to parse it.

• PEMDAS and similar are really a horrible way to teach operator precedence, because that's how you get geniuses claiming `2-2+3 = 2-(2+3) = -3` "because addition before subtraction, durrr"

• PEMDAS and similar are really a horrible way to teach operator precedence, because that's how you get geniuses claiming `2-2+3 = 2-(2+3) = -3` "because addition before subtraction, durrr"
I'm a bigger than I thought! Thank you!

• And judging from that, they should have named it WTP.

Perl is at least write-only, I've no idea how someone can write that, let alone read it.

• I could not imagine by what logic one can get -17. I understood only upon seeing the poll.

Ok operator precedence is only a matter of convention, but why would anyone think giving + higher precedence than - is useful?

• There are only two operations! Multiplication and addition.

3-3x6+2 = 3 + (-3x6) + 2 = 3 + (-18) + 2 = -13

• I've no idea how someone can write that, let alone read it.

When I was in university, some of the terminals (connected to a Vax or CDC Cyber or some such, at a blazing 1200 baud, IIRC) had APL symbols on the keyboards and could be switched between ASCII and APL by some arcane sequence of keypresses and/or escape codes sent by the host. Occasionally, one would encounter one that had been left in APL mode, which made it useless until somebody that knew how got it back into ASCII mode.

• -13 is the right answer, and +2 is not horribly off (since some people reject PEMDAS). But both 17 and -17 are truly awfully wrong.

17 or -17 is not awfully wrong. It's wrong, but it's "misplaced a negative sign" wrong and that probably costs you a few points or half the problem's worth on a quiz. +2 is truly awfully wrong because it indicates that you don't fucking know how to math.

some people reject PEMDAS

Yes... idiots who don't fucking know how to math.

• There are only two operations! Multiplication and addition.

You can simplify that further to there being only one operation: addition. You might have to use a counter in that case, though, but hey, that’s addition too.

• Nah, there's just NAND.

• Yes, thats exactly how I think. Therefore I could not understand how people got the wrong result.

The question remains why they thought it is worth introducing separate + and - operations with different precedence.

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