View Poll Results: What is the answer?  
2  28  41.18%  
288  40  58.82%  
Voters: 68. You may not vote on this poll 
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#1
Apr711, 06:44 PM

P: 9

Every forum I've searched this on is split 50/50 between 2 and 288 as the answer. What is your consensus?
People arguing PEMDAS say 288 But if you set the 2 in the equation to x and set the equation equal to 288, x then = 1/72. Thus proving 2 is the correct answer. Thoughts? 


#2
Apr711, 07:02 PM

HW Helper
P: 805

288? Following PEMDAS, I get 2:
48÷2*(9+3) = 48÷2*(12) = 48÷24 = 2 The reason why some people are getting 288 is that they're forgetting that there's an invisible multiply sign in the expression. Honestly though, if I ever saw this I would apply a facepalm. It's not good notation and like you're seeing, it's ambiguous without proper use of parentheses and will confuse people. It's better notation to say [tex]\frac{48}{2(9+3)}[/tex] 


#3
Apr711, 07:04 PM

P: 10




#4
Apr711, 07:09 PM

HW Helper
P: 805

48÷2(9+3) equation
You go left to right? I didn't know that.



#5
Apr711, 07:10 PM

PF Gold
P: 1,160

And this is why you never see ÷ used for any serious purpose...the notation is just awful.
MATLAB and Python say 288. 


#6
Apr711, 07:13 PM

P: 10




#7
Apr711, 07:13 PM

PF Gold
P: 1,160

Edit: too late... 


#8
Apr711, 07:13 PM

HW Helper
P: 805




#9
Apr711, 07:14 PM

Mentor
P: 21,313

I get 288. In the acronym PEMDAS, the M and D operations are at the same priority and the A and S are at the same priority. Arithmetic operations at the same priority are evaluated left to right. So for example, 2 + 5  3 is the same as (2 + 5)  3 = 7  3 = 4, while 2  5 + 3 is the same as (2  5) + 3 = 3 + 3 = 0.
I can't say that I remember my algebra teacher in ninth grade going into quite such detail (in fact, all I remember her telling us was the acronym MDAS, with a mnemonic device of My Dear Aunt Sally), but programming languages such as C, C++, C#, Fortran, Pascal, and others are very specific about operator precedence. For this reason, 48÷2*(12) should be evaluated as if it were written (48÷2)*12 = 24 * 12 = 288. If you really meant [tex]\frac{48}{2(9+3)}[/tex] it should be written as 48/(2(9 + 3)). That forces the multiplication to be performed before the division. 


#10
Apr711, 07:16 PM

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P: 21,313




#11
Apr711, 07:21 PM

P: 3,387

We're taught BODMAS in school.
Same basic principle. Brackets, Orders, Division / Multiplication, Addition / Subtraction. I will add though that my secondary school teachers told us to use that exact order and not that D and M held equal value (and A and S the same). So we'd always do division before multiplication and addition before subtraction. But I doubt that affects things. EDIT: So if I give division priority (as per strictly following the order of BODMAS) after the brackets I get: 48 / 2*(9+3) = 48 / 2*(12) = 24*12 = 288 But if I give multiplication priority (which I'd never do): 48 / 2*(9+3) = 48 / 2*(12) = 48 / 24 = 2 Have I missed something here? Based on BODMAS and following that exact order I agree with 288. So I'd say they were right to say follow the order strictly. 


#12
Apr711, 07:22 PM

P: 10




#13
Apr711, 07:26 PM

Mentor
P: 21,313




#14
Apr711, 07:31 PM

PF Gold
P: 1,160

I wrote a quick C program (it's been a looong time...thankfully I have my K&R) and C also says 288.



#15
Apr711, 07:31 PM

P: 51

This problem also face at my Programming called Tree.
Actually, i am no agree 288 with this answer but i haven't any good reasons because normally you can press the calculator would get 288.Therefore, our tutor said that we have to considered going with the lefthand side when facing the problem with time or divide which going the first, so depended on the question given,for this, we considered the division going first then the answer would get 288. But for me , i will say that the question problem because it haven't make that clear for the packaging. 


#16
Apr711, 07:33 PM

P: 3,387




#17
Apr711, 07:38 PM

P: 9

Looking at it like this though:
48 ÷ x(9 + 3) = 288 48 ÷ 9x + 3x = 288 48/12x = 288 4/x = 288 4 = 288x 4/288 = x 1/72 = x Would suggest that 288 is wrong, and that 2 is correct. Also, with the order of operations aren't we using the distributive property which states as an example: Simplify 16 ÷ 2[8 – 3(4 – 2)] + 1. 16 ÷ 2[8 – 3(4 – 2)] + 1 = 16 ÷ 2[8 – 3(2)] + 1 = 16 ÷ 2[8 – 6] + 1 = 16 ÷ 2[2] + 1 (**) = 16 ÷ 4 + 1 = 4 + 1 = 5 Then, looking at what I have bolded below: The confusing part in the above calculation is how "16 divided by 2[2] + 1" (in the line marked with the doublestar) becomes "16 divided by 4 + 1", instead of "8 times by 2 + 1". That's because, even though multiplication and division are at the same level (so the lefttoright rule should apply), parentheses outrank division, so the first 2 goes with the [2], rather than with the "16 divided by". That is, multiplication that is indicated by placement against parentheses (or brackets, etc) is "stronger" than "regular" multiplication. Typesetting the entire problem in a graphing calculator verifies this hierarchy. Note that different software will process this differently; even different models of Texas Instruments graphing calculators will process this differently. In cases of ambiguity, be very careful of your parentheses, and make your meaning clear. The general consensus among math people is that "multiplication by juxtaposition" (that is, multiplying by just putting things next to each other, rather than using the "×" sign) indicates that the juxtaposed values must be multiplied together before processing other operations. But not all software is programmed this way, and sometimes teachers view things differently. If in doubt, ask! This all seems to point toward 2 being the correct answer. 


#18
Apr711, 07:42 PM

P: 10




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