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Math Problem

Poll: Math Problem (69 member(s) have cast votes)

Answer?

  1. 2 (29 votes [42.03%] - View)

    Percentage of vote: 42.03%

  2. 288 (32 votes [46.38%] - View)

    Percentage of vote: 46.38%

  3. other (8 votes [11.59%] - View)

    Percentage of vote: 11.59%

Vote
Can you solve it and get it right?

48÷2(9+3) = ? :-*

This post has been edited by Kaxbe: 09 April 2011 - 06:09 PM

  • #1
  • 09 April 2011 - 04:47 PM
48/2(9+3)
48/2(12)
24(12)
288
  • #2
  • 09 April 2011 - 05:00 PM
I... think you're missing a set of brackets there. It's kind of ambiguous. :unsure:
  • #3
  • 09 April 2011 - 05:03 PM

View PostStarwatcher, on 09 April 2011 - 05:03 PM, said:

I... think you're missing a set of brackets there. It's kind of ambiguous. :unsure:


Nope
  • #4
  • 09 April 2011 - 05:04 PM
Really? I just need to know order of operations for that one give me harder stuff!
  • #5
  • 09 April 2011 - 05:08 PM
So what do you want us to divide first? The entire 2(9+3), or just by 2 and then multiply by (9+3)?

What is your convention here?

Using the standard order of operations... I think it would be 48/2(12) = 48/24 = 2.

This post has been edited by Starwatcher: 09 April 2011 - 05:13 PM

  • #6
  • 09 April 2011 - 05:10 PM

View PostStarwatcher, on 09 April 2011 - 05:10 PM, said:

So what do you want us to divide first? The entire 2(9+3), or just by 2 and then multiply by (9+3)?

What is your convention here?


Figure it out.


View PostRawrdinosaur, on 09 April 2011 - 05:08 PM, said:

Really? I just need to know order of operations for that one give me harder stuff!


You didn't give an answer. I don't believe you.
  • #7
  • 09 April 2011 - 05:13 PM
Ok order of operations goes like this everything inside brackets first, then multiplication and division starting on the left and going right, and finally addition and subtraction going from left to right.
  • #8
  • 09 April 2011 - 05:13 PM
So easy =P
Using PEMDAS(Parenthesis, ezponents, multiply,divide,add,subtract)
We do what in the parenthesis first 48/2(9+3) becomes 48/2(12)
Then, ummmmmmm. Darn, i'm pretty sure we want to multiple 2(12), so i'll do that.
48/24 now, then some simple division to reach the [suspected] answer of 2
  • #9
  • 09 April 2011 - 05:15 PM
  • Migrant
  • Would refuse to attend a gay wedding; makes out with men
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View PostStarwatcher, on 09 April 2011 - 05:03 PM, said:

I... think you're missing a set of brackets there. It's kind of ambiguous. :unsure:
Yep! It's very ambiguous because we are writting it in the computer, which means using only one line. If you were to write it by hand you might go:
48_ * (9+3) = 288
2

or

__48__ = 2
2 (9+3)

which would clarify things. The way it is written it is just wrong and cannot be solved for certain.

Remember the order of factors does not change the product.

This post has been edited by Migrant: 09 April 2011 - 05:16 PM

  • #10
  • 09 April 2011 - 05:15 PM

View PostKaxbe, on 09 April 2011 - 05:13 PM, said:

View PostStarwatcher, on 09 April 2011 - 05:10 PM, said:

So what do you want us to divide first? The entire 2(9+3), or just by 2 and then multiply by (9+3)?

What is your convention here?


Figure it out.


View PostRawrdinosaur, on 09 April 2011 - 05:08 PM, said:

Really? I just need to know order of operations for that one give me harder stuff!


You didn't give an answer. I don't believe you.


You could be an alien on a distant world, who likes to add before he multiplies. There's nothing wrong with this at all, but you've got to TELL ME what you MEAN when you write one of these statements! Otherwise, it's meaningless!

I used our standard, earthling convention here, where we do brackets first and stuff.

This is like me saying "njdfsnfglkadlwqi !!! pdsfksdfmflks 5463463/24235423+342395634*^&*&^*^&621" and expecting YOU to figure out what I meant. >:O
  • #11
  • 09 April 2011 - 05:18 PM
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I think that means you are just a slight bit irritated, Watcher. ^_^
  • #12
  • 09 April 2011 - 05:21 PM

View PostMigrant, on 09 April 2011 - 05:15 PM, said:

View PostStarwatcher, on 09 April 2011 - 05:03 PM, said:

I... think you're missing a set of brackets there. It's kind of ambiguous. :unsure:
Yep! It's very ambiguous because we are writting it in the computer, which means using only one line. If you were to write it by hand you might go:
48_ * (9+3) = 288
2

or

__48__ = 2
2 (9+3)

which would clarify things. The way it is written it is just wrong and cannot be solved for certain.

Remember the order of factors does not change the product.


It's 48÷2(9+3) = ? not 48÷(2(9+3)) = ?... So after doing the parenthesis, you should just go left to right. Sheesh.
  • #13
  • 09 April 2011 - 05:25 PM

  • #14
  • 09 April 2011 - 05:25 PM
Star doesn't like people messing with his maths :P

What brought up this question anyway Kaxbe?

This post has been edited by matty_batty0: 09 April 2011 - 05:29 PM

  • #15
  • 09 April 2011 - 05:26 PM
So what did I mean kaxbe, what's the answer! Sheesh! Everyone knows that I add 10exp(100) to the result when I divide, that + = - in my convention, and that % means the remainder of integer division. Also, going from left to right is clearly WRONG, so I read from right to left!

Bwahahaha! SQUIRM as you try to guess my convention!

That is this entire problem, summarized. :/

This post has been edited by Starwatcher: 09 April 2011 - 05:32 PM

  • #16
  • 09 April 2011 - 05:30 PM
NoCreativeNames got it right in the second post didn't they?
  • #17
  • 09 April 2011 - 05:32 PM
I'm pretty sure it's 2...


48 ÷ 2(9+3) = ?
9+3 = 12
2(12) = 24

48 ÷ 24 = 2

Could be wrong, though.

This post has been edited by Smash Genesis: 09 April 2011 - 05:36 PM

  • #18
  • 09 April 2011 - 05:34 PM

View PostSmash Genesis, on 09 April 2011 - 05:34 PM, said:

48 ÷ 24 = 2

What?
Edit: I love how you edited the post right before I hit reply. It said 48 / 12 = 2 when I read it.

This post has been edited by NoCreativeNames: 09 April 2011 - 05:38 PM

  • #19
  • 09 April 2011 - 05:36 PM
The correct way to do this is as follows isn't it?
Brackets first
Then indices
Then multiplication and division (they both get equal priority so just go from left to right)
Then addition and subtraction (again both have equal priority so just from left to right)

Have to say, when seeing the level of some of the random stuff talked about on these forums, it is pretty funny to see people tripping over simple mathematics

This post has been edited by matty_batty0: 09 April 2011 - 05:42 PM

  • #20
  • 09 April 2011 - 05:38 PM

View PostSmash Genesis, on 09 April 2011 - 05:34 PM, said:

48 ÷ 2(9+3) = ?
9+3 = 12
2(12) = 24

48 ÷ 24 = 2

Incorrect because you're supposed to divide 48 into groups of 2, and then multiply by 12.
48÷2(12) ≠ 48÷(2[12])

This post has been edited by NoCreativeNames: 09 April 2011 - 05:43 PM

  • #21
  • 09 April 2011 - 05:41 PM

View Poststormthehouse, on 09 April 2011 - 05:15 PM, said:

So easy =P
Using PEMDAS(Parenthesis, ezponents, multiply,divide,add,subtract)
We do what in the parenthesis first 48/2(9+3) becomes 48/2(12)
Then, ummmmmmm. Darn, i'm pretty sure we want to multiple 2(12), so i'll do that.
48/24 now, then some simple division to reach the [suspected] answer of 2


PEMDAS is incorrect. Division is always before Multiplication. Therefore my school used the term BEDMAS

Bracket, exponent, division, multiplication, addition, subtraction.
  • #22
  • 09 April 2011 - 05:42 PM
What really bothers me about this, is that the entire thing is a matter of convention. "correct" and "incorrect" seem to depend on who you ask... it's not like there was some god-given "true" way to write these things down on a computer without brackets, that's why we have them, to remove ambiguity.

These debate things are so annoying, when the only thing at issue, the ONLY source of disagreement, is peoples different conventions.
  • #23
  • 09 April 2011 - 05:45 PM
  • Migrant
  • Would refuse to attend a gay wedding; makes out with men
    Member
There is no correct way people. Left to right is NOT a rule, ever. You can re-write any expresion in any order, as long as you keep the signs and multiplications / divisions correct. The problem here is that expression is badly written.

On another issue, this would never be a real-world problem, as in a real problem you would know whether you are dividing by 2 or by [2*(9+3)].
  • #24
  • 09 April 2011 - 05:46 PM
How about this? type the problem directly into any calculator, bet you will always get an answer of 288. You would expect a calculator of all things to know the "right" way to go about this sort of thing.

This post has been edited by matty_batty0: 09 April 2011 - 05:48 PM

  • #25
  • 09 April 2011 - 05:48 PM
but it was programmed by a human, who just said something like "well, if the schmuck types in a badly formed expression, just assume this that and the other thing to give him a number".

Besides, my calculator gives me a different answer. It uses reverse polish notation instead of brackets.
  • #26
  • 09 April 2011 - 05:52 PM
  • Migrant
  • Would refuse to attend a gay wedding; makes out with men
    Member
Calculators go left to right in abiguous problems. Real maths is never ambiguous.

This post has been edited by Migrant: 09 April 2011 - 05:55 PM

  • #27
  • 09 April 2011 - 05:54 PM
Reverse polish notation? Never even heard of that :unsure: I thought you said

View PostStarwatcher, on 09 April 2011 - 05:18 PM, said:

I used our standard, earthling convention here, where we do brackets first and stuff.

:P
  • #28
  • 09 April 2011 - 05:54 PM

View Postmatty_batty0, on 09 April 2011 - 05:26 PM, said:

Star doesn't like people messing with his maths :P

What brought up this question anyway Kaxbe?


People on, like, five different forums I visit made threads on this... like, a day ago... and it's still going on.
  • #29
  • 09 April 2011 - 05:55 PM
You should make it a poll 8-D

This is rather serious business afterall.

This post has been edited by matty_batty0: 09 April 2011 - 06:00 PM

  • #30
  • 09 April 2011 - 06:00 PM
Well, you could always just use the distributive property.

48/2(9+3)
2x9=18
2x3=6
18+6=24
48/24=2

The answer is 2.

This post has been edited by David: 09 April 2011 - 06:00 PM

  • #31
  • 09 April 2011 - 06:00 PM
48/2(9+3)
48/2(12)
24(12)
288
BEDMAS is what you use for this.

BEDMAS and PEMDAS are the same thing because you are meant to go left to right for multiplication/division and addition/subtraction.

This post has been edited by Wolf: 09 April 2011 - 06:15 PM

  • #32
  • 09 April 2011 - 06:08 PM

deathkilldestroy said:

The two is attached to those parentheses, so it's a single expression, and that's gonna take precedence over that division expression.

This post has been edited by NoCreativeNames: 09 April 2011 - 06:25 PM

  • #33
  • 09 April 2011 - 06:22 PM
Pemdas is king , also the entire thing is 48 over (2x(9+3))

Pemdas is king , also the entire thing is 48 over (2x(9+3)), so u solve the bottom first then divide 48 by 24.
48
------
2(9+3)
  • #34
  • 09 April 2011 - 06:28 PM

View PostNoCreativeNames, on 09 April 2011 - 06:22 PM, said:

deathkilldestroy said:

The two is attached to those parentheses, so it's a single expression, and that's gonna take precedence over that division expression.



Wrong.
  • #35
  • 09 April 2011 - 06:46 PM
This is like the fourth or fifth place I've seen this and it's getting old. :nope:

The answer people give depends on how they interpret the denominator (either as {48/2}*{9+3), or as 48/{2(9+3)}).

The answer is 288, and the reason that people get it wrong is because PEMDAS/BEDMAS/BOMDAS teaches people bad habits and is not universally correct.

The parentheses are used to clarify that nine plus three should be treated as one term, not that it takes precedence over multiplication and division.

This post has been edited by Lariat: 09 April 2011 - 07:49 PM

  • #36
  • 09 April 2011 - 07:05 PM

View PostKaxbe, on 09 April 2011 - 06:46 PM, said:

View PostNoCreativeNames, on 09 April 2011 - 06:22 PM, said:

deathkilldestroy said:

The two is attached to those parentheses, so it's a single expression, and that's gonna take precedence over that division expression.



Wrong.

Indeed. The 2 being beside the ( is the same as there being a multiplication symbol between them. It does not quantify them as a single "unit."
  • #37
  • 09 April 2011 - 07:38 PM
Ok I'm gonna prove that 2=1 there by negating all attempts to solve this problem

a = b
a^2= ab
a^2 - b^2 = ab - b^2
(a - b)(a + b) = b(a - b)
a + b = b
b + b = b
2b = b
2 = 1

So since I have proven 2=1 the answer to this problem is now 4 because
48/1(9+3)
48/12
4

This post has been edited by Rawrdinosaur: 09 April 2011 - 07:55 PM

  • #38
  • 09 April 2011 - 07:52 PM
  • Migrant
  • Would refuse to attend a gay wedding; makes out with men
    Member
I love those expressions, rawrdinosaur :P
The trouble of course is that from the fourth to the fifth step you devided everything by (a - b), but a - b = 0 and by dividing by 0 you make a mathematical error which causes all numbers to be the same.
  • #39
  • 09 April 2011 - 08:20 PM

View PostMigrant, on 09 April 2011 - 08:20 PM, said:

I love those expressions, rawrdinosaur :P
The trouble of course is that from the fourth to the fifth step you devided everything by (a - b), but a - b = 0 and by dividing by 0 you make a mathematical error which causes all numbers to be the same.


Congratulations your are intelligent. Yes that is the one flaw in the proof. I was hoping it would take longer for anyone to figure it out.
  • #40
  • 09 April 2011 - 08:53 PM
Was Starwatcher arguing maths is ambgiuous? That maths is based on opinion?

If that were true, the whole universe would look different to everyone depending on who looked at it.

This post has been edited by The Nturtanyr: 09 April 2011 - 11:25 PM

  • #41
  • 09 April 2011 - 11:25 PM

View PostThe Nturtanyr, on 09 April 2011 - 11:25 PM, said:

Was Starwatcher arguing maths is ambgiuous? That maths is based on opinion?

If that were true, the whole universe would look different to everyone depending on who looked at it.


No, please... have another look at my posts. Math is just fine, what I was going on about was that the SYMBOLS we use to describe it have to be described unambiguously.

The problem here is someone wrote something down that could be read at least 2 different ways. That just means the question wasn't well-posed, not that all math and science is relative.

This post has been edited by Starwatcher: 09 April 2011 - 11:58 PM

  • #42
  • 09 April 2011 - 11:53 PM
But from what I know, I'm pretty sure math is straight forward in its symbols. Order has been stated for years, you can't say it changes from person to person.
  • #43
  • 10 April 2011 - 02:43 AM
That's just a definition, not an objective fact. Really, the only disagreement here is about typesetting.

This post has been edited by Starwatcher: 10 April 2011 - 02:53 AM

  • #44
  • 10 April 2011 - 02:52 AM

View PostStarwatcher, on 10 April 2011 - 02:52 AM, said:

Really, the only disagreement here is about typesetting.

I agree. While I believe one interpretation is wrong according to standard conventions, the disagreement is over the convention, not the math.

Although our eyes look at "2(9+3)" and want to treat it as one term, it should be treated as 2 multiplied by the term (9+3).

Interpreted, the equation is "(48)/(2)*(9+3)", not "(48)/[2(9+3)]".

This post has been edited by Lariat: 10 April 2011 - 03:05 AM

  • #45
  • 10 April 2011 - 03:05 AM
Didn't I just see this on Facepunch yesterday? Why is it all over them internets?
  • #46
  • 10 April 2011 - 04:03 AM
I got 8.666666666666667.
  • #47
  • 10 April 2011 - 04:31 AM
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48÷2(9+3)
Without a doubt, the parenthesis make the first move clear.
48÷2*12
At this point, one must choose between the order of operations that goes based on symbols only,( () then * then ÷ then + then - ) and the system that goes based on groupings with a secondary system of right to left( () then * and ÷ then + and -). In the first system we always multiply before we divide and in the second system we chose the right most of multipliers and dividers.
48÷24 or 24*12
2 or 288
The issue is, I have heard of it being done both ways it it would be immposable to test because anything created to test either one would always be correct in the one it was made for and incorrect in the other.

View PostMikaro, on 10 April 2011 - 04:31 AM, said:

I got 8.666666666666667.

You used a calculator then didn't you?
Either show your work or post your exact input.
  • #48
  • 10 April 2011 - 04:49 AM
I would but so many people have answered it above me so how do you know I haven't cheated?
  • #49
  • 10 April 2011 - 04:49 AM
* and / have the same precedence, as do + and -. () has the highest precedence.

Hence, first the brackets, then the division, then the multiplication.
  • #50
  • 10 April 2011 - 05:00 AM
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