48÷2(9+3) = ?

[Quattro Pete]

Originally Posted By: d00df00d
(48 / 2) * (9 + 3).

The first set of parenthesis in this notation is redundant since you would perform this 48/2 division first anyway (going from left to right). But I do understand your point.

 

[ZeeOSix]

The inputs from math experts:

http://www.mymathforum.com/viewtopic.php?f=13&t=20187

You can NOT use the distributive rule as the equation is written.


There is nothing in the order of operations that says you have to do a distributive operation first. Even if you did, the "2 crowd" is still violating the O of Os. This is how the guys who think the distributive operation done first are screwing up.

48÷2(9+3) =

48÷2(9)+2(3) = O of Os have already been broken due to multiplication 1st, and not the parenthesis operation 1st

48÷18+6 =

48÷24 = 2 because addition was done before division with the lack of parenthesis

IF the O of Os were followed after the distributive move, then the answer would actually be 8.66666 ....

 

[mechanicx]

Originally Posted By: ZeeOSix
Originally Posted By: wallyuwl
The three notations you used above come up with the same answer in isolation, but as part of a larger problem they don't because without an "x" or asterisk between the 2 and parentheses you need to use the distributive property.


Forgot to say ... show some proof that the distributive property over rides the order of operations rules. I've searched high and low and can't find anything that talks about it. Can you?

The way the equation 48÷2(9+3) = ? is written, the order of operations says you must resolve what's in parentheses first and then do division and multiplication from left to right.

If you magically decide to do the distributive property 1st, then you are doing multiplication first and then on top of it doing addition before division

, which strictly goes against the O of O.

In order for this equation to equal 2 and follow the O of Os, it would have to be written as 48÷[2(9+3)] = ?



I know I'm being redundant here, but so is the other side so bear with me. For those in the "perform distibution first" crowd, why just distribute the 2? 48/2 (or 24)is also outside and next to the parentheses so why not distribute the whole shebang "to get rid of the parentheses"?

Distibuting 48/2:

48/2*9+48/2*3=

216+72=

Well darn it still equals 288 performing distribution first

.

Wait let's just distribute the 2 first to get rid of the parentheses:
48/18+6=
8.6666

Still not 2

.

 

[ktrsb]

2

Wait, what?

 

[asiancivicmaniac]

My TI-89 tells me it's 288, but if I did it by hand I would have picked 2. But then again I was never good at math.

 

[KrisZ]

Holy revival thread batman

 

[TacoToy]

PEMDAS is a mnemonic device that is misleading to some individuals as they are falsely led to believe that multiplication is always performed before division, and addition is always performed before subtraction.

In the problem 48 - 2 + 3, the subtraction is done first, and then the addition is performed to give a result of 49.

For the original problem of 48/2(9 + 3), if one views division by 2 as being equivalent to multiplying by 1/2, then
48/2(9 + 3) = 48*(1/2)*(9+3) = 48*(1/2)*12 = 24*12 = 288.

 

[Al]

I went back to my old (college engineering texts) they don't follow protocol.

 

[Pablo]

ooops sorry, I thought this was the investment thread, sorry, excuse me, sorry.....

 

[Vikas]

Please, don't start this again!!

 

[mechtech2]

Originally Posted By: bigmike
I found this pretty funny:

This is significant.
I lean towards 2 as the answer, as written.

 

[PandaBear]

This is a reminder why we should always put a parenthesis on both side of a divide, instead of letting the order be "assumed".

How about 48/2*12, is it (48/2)*12? or 48/(2*12)? It depends on the machine that parse it. C programming language will assume from the back to the front when operators have identical precedences. Many candidates got thrown out of interviews because they fail this, and many software crashes because of similar errors.