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Absolute DS

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Source: — Data Sufficiency |
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by goyalsau » Mon Dec 13, 2010 6:39 am
gmatusa2010 wrote:Is |X|= A-B?

1) X=A-B
2) X=B-A

|X|= A-B { Absolute value of X always equal to A - B or Not equal to A - B }

Still trying to understand the logic if absolute value DS.
1) X = A - B { B = 3 , A = -2 }

X = -2 -3 , X = -5 , 5 =/ ( not equal to ) A - B

X = A - B { A = 3 , B = 2 }

X = 3 - 2 , X = 1 , 1 = A - B

X can be positive or negative ,

Not sufficient

2 ) X = B - A apply same operation still not sufficient

Combining statements

B - A = A - B

2B = 2A , B = A

If A = B , A - B , Will always be Zero So | X | = A - B , or x = 0

thus sufficient

My answer is C
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by diebeatsthegmat » Tue Dec 14, 2010 7:28 am
gmatusa2010 wrote:Is |X|= A-B?

1) X=A-B
2) X=B-A

Still trying to understand the logic if absolute value DS.
if x> 0 so |x|=A-B but if x<0 |x|=B-A
from above, you can see that both are sufficient
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by tomada » Tue Dec 14, 2010 12:04 pm
When you say both are sufficient, do you mean that each one is sufficient, or that the combination of statements is sufficient?

diebeatsthegmat wrote:
gmatusa2010 wrote:Is |X|= A-B?

1) X=A-B
2) X=B-A

Still trying to understand the logic if absolute value DS.
if x> 0 so |x|=A-B but if x<0 |x|=B-A
from above, you can see that both are sufficient
I'm really old, but I'll never be too old to become more educated.
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by diebeatsthegmat » Wed Dec 15, 2010 8:46 am
tomada wrote:When you say both are sufficient, do you mean that each one is sufficient, or that the combination of statements is sufficient?

diebeatsthegmat wrote:
gmatusa2010 wrote:Is |X|= A-B?

1) X=A-B
2) X=B-A

Still trying to understand the logic if absolute value DS.
if x> 0 so |x|=A-B but if x<0 |x|=B-A
from above, you can see that both are sufficient
no, my english is bad, its ENGRISH :)... i meant C
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by Zerks87 » Wed Jan 19, 2011 11:15 am
When I did this question I did it a little differently.

The question is: Is abs. x = a - b, so are both x and -x = a - b

(1) x = a - b. From this we know that positive x = a - b, but -x = b - a. Therefore since one is and one isn't that means the absolute value of x cannot = a - b. Which is sufficient to answer the question

(2) x = b - a. The same logic applies except in reverse because positive x obviously cannot = a - b because it says it = b- a, but negative x = a-b, so since one scenario works and one does not, abs. x cannot = a - b. SuFF

Therefore my answer would be D
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by gmat1011 » Wed Jan 19, 2011 9:09 pm
D in my book

Q basically asks:

is X = A-B OR X = B-A?

If we can get either answer from each stem then sufficient.

Stem 1: Sufficient

Stem 2: Sufficient
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by gmat1011 » Wed Jan 19, 2011 9:15 pm
sheesh... yeah should be C

we don't know if A>B or B>A... So stems can yield y and no...

i agree should be C.
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by sushantgupta » Mon Jul 04, 2011 11:46 am
both together are sufficeint
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by Sanjay2706 » Mon Jul 04, 2011 8:40 pm
IMO D
OA?
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by kevincanspain » Mon Jul 04, 2011 10:39 pm
gmatusa2010 wrote:Is |X|= A-B?

1) X=A-B
2) X=B-A

Still trying to understand the logic if absolute value DS.
(1) reduces the question to the following: is |a-b| = a - b ?

Note that |x| is not equal to both x and -x unless x= 0

If x > 0 |x| = x but if x < 0 , |x| = - x

Thus |a-b|= a-b if and only if a-b >= 0

NOT SUFF

(2) |b-a| = a - b =-(b -a) if and only if b - a >=0 i.e. a - b <= 0

NOT SUFF

(T) a-b must be a real number. If it is positive or zero, (1) tells us that the answer is yes, whereas if it is negative, (2) tells us the answer is yes. SUFF

Alternatively , together we see that a - b = b - a . Thus a = b and x = 0 SUFF
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by shingik » Sun Sep 18, 2011 2:24 pm
The given statement implies x = a-b OR x = -(a-b) (which is equivalent to x = b-a). This is a ten second problem if you know this method because you know that one solution is NOT enough. Since the choices give only one solution each so the answer MUST be C or E. C is the answer because 1 and 2 provide each of the solutions/equations you want. The math behind it does not matter that much if you know how to break down absolute value statements i.e it is not necessary to beat yourself over the head trying to figure out the signs and what not. I have started truly studying now and it is begining to pay off---aluta continua!!!! (lol).
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by Taran » Thu Oct 13, 2011 10:48 pm
Is |X|= A-B?

Stmt1: X=A-B; Say A=3 and B=2. A-B will be 1, i,e X=1 and thus |X| will remain 1. Thus in this case |X| is equal to X or A-B. Now take A=2 and B=3. A-B will be -1, i.e X=-1 and thus |X| will become 1. |X| is not equal to X or A-B in this case. Two results, NOT SUFFICIENT.

Stmt2: Do the same as above and you will get two results. NOT SUFFICIENT.

Let's take the two statements together now.
X=A-B as well as B-A. i.e A-B=B-A or 2A=2B or A=B. Now image a number line and place points A and B on it. Since both A and B are same, it doesnt matter whether you put A-B or B-A. Their difference will always be ZERO. Thus x will always be ZERO or |X| will always be ZERO. Therefore, |X| will always be equal to X or A-B. SUFFICIENT.
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by GmatKiss » Sat Oct 15, 2011 7:20 am
IMO:C
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by saketk » Tue Oct 18, 2011 2:19 am
gmatusa2010 wrote:Is |X|= A-B?

1) X=A-B
2) X=B-A

Still trying to understand the logic if absolute value DS.
We can also do this question by assuming values for A and B resp.

Statement 1: -

let A=2 and B =1
then X = 1 which is equal to |x|

but if we take A = 1 and B =2
then X= -1 which is not equal to |x|,which is always positive

Hence stmt 1 is NOT SUFFICIENT

Similarly we can show that Statement 2 by itself is not sufficient.

Combine the 2 statements we will get

A-B = B-A

or A =B. This implies that value of X = 0

Therefore we need both statements together to answer this question

OPTION C
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