48÷2(9+3) =

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irishScott

Lifer
Oct 10, 2006
21,568
3
0
Except that multiplications and divisions have the same precedence. The stupid acronym was made up so that stupid kids would remember, apparently they failed to remember that division and multiplication are calculated in order of appearance.

 

DrPizza

Administrator Elite Member Goat Whisperer
Mar 5, 2001
49,606
166
111
www.slatebrookfarm.com
Ok, basically add Matthisa and DrPizza to the "it's ambiguous and could be 2" group. I'm still not buying it.

Lol, I might be on shaky ground going up against anyone with "Math" right in his user name, and I would readily concede that the esteemed Doctor is, in general, 1000 times the mathelete that I am or ever was, but, HEY DOC! RESPOND TO THESE:



More pithily:



<-------------- Runs and hides. Though he did quite well in math on his SAT's, has never had a math class above HS calculus, which I somehow got a A in even while still employing my standard HS method of not doing homework and just cramming before each exam. Calc was BY FAR the hardest HS subject to do this for. I'm still amazed my approach worked. It almost literally hurt my head, and I promptly forgot EVERYTHING!

As for Matthisa, I have seen you try to overgeneralize from ONE failed calculator (TI85), even after TI's own bulletin explaining their FAILURE was posted, plus many references to the rarified math circles in which you circulate.

Ok, how 'bout posting links with quotes from recognized and credentialed math mavens on this crucial, crucial subject.
Okay, here's the response:
I believe that the best answer is 288. It's a very poorly formed expression. I can't recall ever seeing any math textbook forming an expression that way. Sometimes, parentheses are implied ex: 2/xy But, whether or not parentheses are implied when mixing numerals and variables is rather ambiguous. I would never trust a TI calculator, or any programming language (that understood 2x means 2 times x) to perform an operation with a poorly defined function.

Math people aren't generally sloppy. If they mean "two-thirds x", they're not going to write it 2/3x; they'll write it (2/3)x. Likewise, I'd hope that most would write 2/(3x) if that's what they mean.
 

Perknose

Forum Director & Omnipotent Overlord
Forum Director
Oct 9, 1999
46,441
9,665
146
Okay, here's the response:
I believe that the best answer is 288.

Thanks DrP! I'm a busy and important man. so naturally I read no further. :awe:

Seriously, though, while I can see your point, I still don't see any legitimate way to conclude that the answer is any other than 288, which makes it, in my eyes, the only answer.

But mostly I'm glad that you didn't use your qualitatively superior math skill and knowledge to pull my pants down and point, so to speak, around this.
 

dust

Golden Member
Oct 13, 2008
1,339
2
71
It seems to me that 288 is the right answer for ~90% of the time.

However, I really like 8, is 8 taken?
 

GoPackGo

Diamond Member
Oct 10, 2003
6,448
523
126
You have all assumed its a Base 10 number system...what if its Hex..Base 16? The answer is 1B0!
 

rchiu

Diamond Member
Jun 8, 2002
3,846
0
0
Geeks would say 288 and laugh at people who answered 2.

People who deal with real problems in real world know writing equation that way is dumb and simply asking for trouble.
 

C1

Platinum Member
Feb 21, 2008
2,339
89
91
Saw this problem [ie, 48÷2(9+3) = ? ] posted on GLP today.

I suspected correctly that this classic would also be discussed on AT.

If you would follow the guidelines of an HP scientific calculator user guide, then the answer would be "2" (ie, work first from inside the parentheses; I also think that standard high level coding such as FORTRAN or BASIC would perform the same).

However, the real answer seems to be that the result is indeterminate.

There are some real good lessons here (some which I had forgotten):

https://math.berkeley.edu/~gbergman/misc/numbers/ord_ops.html
 

Childs

Lifer
Jul 9, 2000
11,450
7
81
Saw this problem [ie, 48÷2(9+3) = ? ] posted on GLP today.

I suspected correctly that this classic would also be discussed on AT.

If you would follow the guidelines of an HP scientific calculator user guide, then the answer would be "2" (ie, work first from inside the parentheses; I also think that standard high level coding such as FORTRAN or BASIC would perform the same).

However, the real answer seems to be that the result is indeterminate.

There are some real good lessons here (some which I had forgotten):

https://math.berkeley.edu/~gbergman/misc/numbers/ord_ops.html

When I first saw it I interpreted it as essentially a/bc. b(c) had implied parentheses making it one value. But then I figured if someone is using parentheses in one place and not another, that is intentional. Anyways, it was ambiguous enough that I didnt vote on the poll. lol
 
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