199 réponses à ce sujet

[Macrake]

Kronner wrote...

Macrake wrote...

48/2x12 is NOT the same as 48/2(12).

LOL
Of course it is. This is elementary school stuff. Geez.

48 / 2 * 12 IS THE SAME as 48 / 2 * (12)

Nope. Sure 2(12) is calculated as 2x12. But the () means you have to do that calculation before simply removing the ().

[Kronner]

Macrake wrote...

Kronner wrote...

Macrake wrote...

48/2x12 is NOT the same as 48/2(12).

LOL
Of course it is. This is elementary school stuff. Geez.

48 / 2 * 12 IS THE SAME as 48 / 2 * (12)

Nope. Sure 2(12) is calculated as 2x12. But the () means you have to do that calculation before simply removing the ().

Wanna bet? I still can't believe you actually believe that.

(48) / (2) * (12) is equal to 48 / 2 * (12), which is also equal to 48 / 2 * 12
In other words, brackets are irrelevant here.

Everyone who passed elementary school must know that.

Modifié par Kronner, 09 avril 2011 - 09:55 .

[phoenixofthunder]

There is a different method to arrive at this answer that I have as of yet to see here. Following this line of mathematics is easier mentally for me.
First off the math I'm about to use is not what most people are used to by a long shot.

In it:
Multiplying by 6 IS EQUAL TO dividing by 2
The operator in parenthesis' gets reversed ("+" becomes "-" & vicea versa)("*"becomes"÷" & vicea versa). Plus ignored when an opposing operator is also part of the equation.

So following that reasoning:
÷2 becomes *6
(9+3) gets ignored. Due to division operator.

Following this reasoning:
48*6=288

Proof it works & forums for this methodology. 
1&2

[Kaiser Arian XVII]

howdy rookie!
first you need to distinguish important parts of this math junk: 48÷2(9+3)
firstly 9+3=12
=> 48÷2(12)
then => 2*12=24
=> 48÷24 that becomes
=> 48÷24=2
2 is the answer. and don't forget that you must do all these calculations in your mind.

[phoenixofthunder]

Garbage Master wrote...
howdy rookie!
first you need to distinguish important parts of this math junk: 48÷2(9+3)
firstly 9+3=12
=> 48÷2(12)
then => 2*12=24
=> 48÷24 that becomes
=> 48÷24=2
2 is the answer. and don't forget that you must do all these calculations in your mind.

Rose of Mars wrote...

People! This is 4th grade math! C'mon!

FIRST: Solve the (9+3). You will end with 48/2*12

Remember: theres a multiplication signal implied between the 2 and the (9+3). Now that we solved the parenthesis part, we solve the expression the normal way. which is... always solve these operations from the LEFT.

Don't believe me? Wolfram Alpha's site. A REAL mathematician's site, not the "almighty" flawed Google calculator we are so dependent.

http://www.wolframal...ut/?i=48÷2(9+3)

<_<

Modifié par phoenixofthunder, 10 avril 2011 - 11:54 .

[ejoslin]

/pounds head against wall. /whispers "Order of Operations...."

I am seriously hoping that the people who are insisting the answer is "2" are not in any type of engineering program...

To make it clear, there is NO indication in the problem that you multiply 2*12 before the division part of the problem. The 2 is NOT in the parentheses. The 2 is outside of the parentheses. Any pairing you see there is due to endless FOIL drills or something....

48/2(3+9) is NOT NOT NOT equal to 48/[2(9+3)]

Once you start dealing with nestled equations in multiple parentheses, you're going to be in big trouble if you do not understand this. You solve what is INSIDE the parentheses first. In the equation 48/2(3+9) what is in the parentheses is 9+3. That is IT. The 2 is outside of it. So you divide 48 by 2 *FIRST because it's on the left hand side of the equation.

*sigh* My umpteenth post, same as my first...

Modifié par ejoslin, 10 avril 2011 - 05:50 .

[phoenixofthunder]

ejoslin wrote...

/pounds head against wall. /whispers "Order of Operations...."

I am seriously hoping that the people who are insisting the answer is "2" are not in any type of engineering program...

To make it clear, there is NO indication in the problem that you multiply 2*12 before the division part of the problem. The 2 is NOT in the parentheses. The 2 is outside of the parentheses. Any pairing you see there is due to endless FOIL drills or something....

48/2(3+9) is NOT NOT NOT equal to 48/[2(9+3)]

Once you start dealing with nestled equations in multiple parentheses, you're going to be in big trouble if you do not understand this. You solve what is INSIDE the parentheses first. In the equation 48/2(3+9) what is in the parentheses is 9+3. That is IT. The 2 is outside of it. So you divide 48 by 2 *FIRST because it's on the left hand side of the equation.

*sigh* My umpteenth post, same as my first...

Uploaded with photobucket

Modifié par phoenixofthunder, 10 avril 2011 - 06:45 .

[Wicked 702]

ejoslin wrote...

That would be me.  I really have nothing more to add to this whole thing, but I wanted to take my little bow anyway

I wouldn't add the paretheses here -- the equation is not at all ambiguous, though it's a bit confusing if you don't think of the order of operations.  I blame beginning algebra for much of the confusion. 

Credit well deserved.

Edit: And to throw my 2 cents of flame in, just like ejoslin said the "P" in PEMDAS means to do things INSIDE the parenthesis first. Terms outside are treated like any other normal item and are not subject to the whims of the parenthesis. Once you add the (9+3) the parenthetical term is completely solved, essentially disappears, and becomes simple left-to-right multiplication/division, yielding the proper answer of 288.

Modifié par Wicked 702, 11 avril 2011 - 09:59 .

[Dominus]

lol over 180 posts over a mathematical question. Oh, you guys...(and girls. Hello, ladies.)

[Godak]

Again...why in the world was this even asked? XD

[AngryFrozenWater]

I am glad to see that this thread is still going strong.

My answer: 288. Obviously.

Edit: Since I am a C++ software engineer I should actually say 0x120 to confuse most of you. Which is really the correct answer too.

Modifié par AngryFrozenWater, 12 avril 2011 - 11:53 .

[Kaiser Arian XVII]

ah bull****! every engineer in our family says the answer is 2, and this is an elementary math (1998 class). I must remind that 48 lies on ____ and 2(9+3) under it. ____ is equal to ÷. and () must be dealt with first. so we can calculate:
1) 2x9+2x3=18+6=24
or 2) 2x(9+3)= 2x12=24
=> so 48 ____ 24 / 48÷24=2
also 48/2(3+9) is equal to 48/[2(9+3)]
Looks like my English has become rustier! I will login just to make sure you understand it!

[AngryFrozenWater]

Show those "engineers" this link:

http://www.wolframal...ut/?i=48÷2(9+3)

Modifié par AngryFrozenWater, 12 avril 2011 - 12:16 .

[Kaiser Arian XVII]

your logic is falsch

[AlexMBrennan]

Seriously now - was that a trick question cunningly crafted by psychologists somewhere? Because I read that at first as "48 over 2(9+3)" and missed the implied multiplication "48÷2 x (9+3)"

Edit: Just look at Mathematica's inline evaluation of the input:
48
--- (9+3) = 288
2

Modifié par AlexMBrennan, 12 avril 2011 - 12:30 .

[Kaiser Arian XVII]

psychologists can go to ...!
48
--- (9+3) = 288
2
is true but every student must know that 2(9+3) is different and is at higher position and must be calculated first. it is simply: 48÷2(9+3). you cant (must not) separate 2 from (9+3)

[AlexMBrennan]

Your statement is false - I'm a undergrad Maths student and I've never heard of it. That's probably because humans, and Mathematica, is capable of handling fractions whilst (some/most? older) calculators and this forum are not. I don't think order of multiplication should matter since real number with usual addition and multiplication form a field which inherits the associativity for multiplication and division (i.e. multiplication by its inverse)

If you have any sources for that claim that implicit multiplication has greater precedence than explicit multiplication then please post it. All I found is a TI KB entry explaining why (newer) TI calculators treat, by convention, implicit multiplication with higher precedence (to reduce the amount of brackets since one cannot enter fractions graphically).

Modifié par AlexMBrennan, 12 avril 2011 - 04:54 .

[OBakaSama]

Interesting to see the different viewpoints expressed in the thread so far. We've had arguments regarding the order of calculation though I assume both sides follow the standard procedure in mathematics.

I would just like to use an analogous formula which retains the same ambiguity of the original:

If y = 4 then:

1/2y = ?

What are your answers and how does that compare to the original?

[AlexMBrennan]

My answer remains that ab/cd = (abd)/© but it's really your fault for using an ambiguous notation. Where do you even find expressions like that? I (Maths undergrad) have never seen anything like that - formulae are always given in as

\\frac{ab}{cd}

or

ab(cd)^{-1}

(Latex syntax, copy and paste the code e.g. here if you can't see how it's supposed to look)

Modifié par AlexMBrennan, 12 avril 2011 - 05:05 .

[Wittand25]

OBakaSama wrote...

Interesting to see the different viewpoints expressed in the thread so far. We've had arguments regarding the order of calculation though I assume both sides follow the standard procedure in mathematics.

I would just like to use an analogous formula which retains the same ambiguity of the original:

If y = 4 then:

1/2y = ?

What are your answers and how does that compare to the original?

2
1/2*4=(2^-1)*(2^2)=2^(2-1)=2^1=2

as long as there are no brackets, y is not part of the denominator. This is exactly the reason why in maths division is eiter handled  by fractions using a horizontal dash or by negative exponents.

[OBakaSama]

That's an interesting answer. I'm trying to tease out the intuitions and assumptions people are using. Be interested to see how others respond.

EDIT: the original was ambiguous without a doubt; though not many participants have really emphasised that though.

Modifié par OBakaSama, 12 avril 2011 - 07:57 .