48÷2(9+3) = ??

Saw this on another forum, then was amazed at the near 50/50 split on the answers.

No name-calling or vicious arguing over a stupid math problem... i'm just curious to see what the majority here is.

In reply to 92CelicaHalfTrac: 2

In reply to 92CelicaHalfTrac:

uh...

48/2(9+3)... PEMDAS says the next step is... (2x9 + 2x3)? izzat right?

288

madmallard wrote: In reply to 92CelicaHalfTrac: uh... 48/2(9+3)... PEMDAS says the next step is... (2x9 + 2x3)? izzat right?

PEMDAS doesn't necessarily speak to that... PEMDAS says to solve what's INSIDE the parantheses first.

But.... you've stumbled upon the part of the equation that creates the disparity between answers.

2

but I don't like how the ÷ is mixed with the dropped x sign.

48 ÷ 2 x (9+3)

or

48/2(9+3)

would be better.

edit- now I get the confusion.

it's either 48 divided by 2 times 12 (288) Or 48 divided by 2*12 (2).....

that's exactly why you don't mix the methods of signage.

Based on the way it's signed, I would call it :

24(12).

Derick Freese wrote: 288

I concur...

As written: 288

Order of operations are as follows (simplified):
1. Anything within parentheses
(2 exponents or roots; not necessary here)
3. Multiplication/Division from left to right. Number with parenthesis next to it implies multiplication.
4. Addition/Subtraction from left to right

http://en.wikipedia.org/wiki/Order_of_operations

I say 2, but I'll ask my 13 year old what she says.

I believe it is 288.

You do the parentheses first, then you do multiplication and division from left to right. So you do the 9+3 first. Then you have 48/2x12. Left to right, you do the 48/2 first, so you have 24x12. 288.

I think it would be better written (48/2)(9+3) if I understand it right.

Dunno. Math isn't my thing. But that's how I recall it.

It is 288, but it could be written more clearly.

PEMDAS god, i'm not liking this......it's like 9th grade all over again lol

you want to do the parenthesis first, so 9+3=12, then since there is a whole number, 12, in the parenthesis, you just take them away which leaves, 48 / 2 x 12. Since the multiply and divide are together you can do whichever is first, so it is 48/2 first which =24, then 24 x 12= 288

288 is my answer as well.

Google's built-in math feature agrees, interestingly it interprets the problem as
(48 ÷ 2) * (9 + 3) = 288

288

9+3=12; 48/2*12 = (48 / 2) * 12 = 288

Wow, this formatting sucks.

But.... with the way the parantheses are used...

Wouldn't 2(12) be considered one number? Or that the two was merely factored out of (9+3)?

My problem is that while i agree that 2(9+3) = 2 x (9+3) as a standalone equation, i don't see it as the same thing within a larger equation.

However, i do agree that the equation is written poorly, and that there are potentially more than one correct answer.

read my revised post

92CelicaHalfTrac wrote: But.... with the way the parantheses are used... Wouldn't 2(12) be considered one number? Or that the two was merely factored out of (9+3)?

Nope. 2(12) has the same precedent as 212. So it won't happen before the division to the left, it's 48/212.

Stupid new math

Old math says 2.

As written in the topic title the answer would be 2.

PEMDAS must be done in order multiplications are done before division and additions are done before subtractions. One can get around this if additative and multiplicative inverses are done correctly.

But, to rewrite the original expression in a format easily readable on the forum and following PEMDAS the expression would be as follows 48/(2(9+3))=2

EDIT:

Another way to look at this is to somewhat ignore PEMDAS and use the distributive property so 2(9+3)=(18+6)=24 therefrore 48/24=2

PEMDAS

I think this is the problem. That's the right order, but within that order, as I understand it, some are on the same level. Multiplication and Division, for instance, are the same. You do them from left to right. The abbreviation is just to help you remember. It isn't the rule. The rule has a little more to it. Please Excuse My Dear Aunt Sally is just to help you remember the broad strokes for the test.

If it was 6/2x3 you wouldn't do the 2x3 first. You'd do them in order left to right. Addition and subtraction are the same way.

Brotus7 wrote:

92CelicaHalfTrac wrote: But.... with the way the parantheses are used... Wouldn't 2(12) be considered one number? Or that the two was merely factored out of (9+3)?

Nope. 2(12) has the same precedent as 2*12. So it won't happen before the division to the left, it's 48/2*12.

To play Devil's Advocate...

Then why was it not written as 2 x (9+3)?

I was always taught through high school and college-level math that the parantheses have to go away first. Solve WITHIN them first, then resolve them before you move on. Resolving them didn't mean simply replacing with an "x."

It boils down to a badly written equation... but it's interesting to me the different interpretations, and it seems to stem from if you stay with basic PEMDAS, or apply algebra "solve for x" logic.

I thought, at least I remember, when you have both multiplication and a divide next to each other, it's just whichever ones first, disregarding the PEMDAS for that moment??

fast eddie, you are correct

2

You'd only multiply through the 2 to the 9 and 3 if they were dissimilar terms, e.g. if it was 2(9k+3j).

EDIT: NO, I take it back. Multiplication and division have the same priority, and are done left to right.

So, after you do the parentheses, it's left to right, 48 / 2 x 12, so 288.

Now, let's kick it up a notch.

2