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madhur_ahuja
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Is |x| = y-z
Source: Beat The GMAT — Data Sufficiency |
IMO Cmadhur_ahuja wrote:Is |x| = y-z ?
1. x + y = z
2. x < 0
1) x=z-y
|x| = y-z, when z<y
|x| = z-y when z>=y, NOT SUFF
2) x<0, no info about y and z, not suff
combined
x=z-y<0
z<y
SUFF
The powers of two are bloody impolite!!
When you have modulus |x| = a, then x can be
X = +a
Or
X = -a
I’m not sure but the answer should be A. The question can be rephrased as:
X = y – z
OR
X = -y + z
From 1 we do get x = -y + z
X = +a
Or
X = -a
I’m not sure but the answer should be A. The question can be rephrased as:
X = y – z
OR
X = -y + z
From 1 we do get x = -y + z
madhur_ahuja wrote:Is |x| = y-z ?
1. x + y = z
2. x < 0
Lets say question ismehravikas wrote:When you have modulus |x| = a, then x can be
X = +a
Or
X = -a
I’m not sure but the answer should be A. The question can be rephrased as:
X = y – z
OR
X = -y + z
From 1 we do get x = -y + z
madhur_ahuja wrote:Is |x| = y-z ?
1. x + y = z
2. x < 0
Is |x| =a
1. x=-a
2. x <0
Don't you think we both require 1 and 2. Since with 1 only we are proving that x=-a for both x<0 and x>0, which is wrong.
only statement 1 should be enoughmadhur_ahuja wrote:
Lets say question is
Is |x| =a
1. x=-a
2. x <0
Don't you think we both require 1 and 2. Since with 1 only we are proving that x=-a for both x<0 and x>0, which is wrong.
stment 1: x=-a
=>|x|=|-a|=a
sufficient
stment 2: x<0 not sufficient
scooby,scoobydooby wrote:only statement 1 should be enoughmadhur_ahuja wrote:
Lets say question is
Is |x| =a
1. x=-a
2. x <0
Don't you think we both require 1 and 2. Since with 1 only we are proving that x=-a for both x<0 and x>0, which is wrong.
stment 1: x=-a
=>|x|=|-a|=a
sufficient
stment 2: x<0 not sufficient
I don't think so
stment 1: x=-a
=>|x|=|-a|=a
thats when a is positive
when a is negative, it will not hold true.
what you are doing wrong is this:
x=-a
|x|=|-a|=a (no, this is wrong)
|x|=|-1|*|a| =|a|
and this will be a or -a depending upon whether a is positive or negative
The powers of two are bloody impolite!!
madhur_ahuja wrote:Is |x| = y-z ?
1. x + y = z
2. x < 0
would go with C.
Is |x| = y-z ?
|x| always >0
=>y-z>0
=>y>z?
stment 1. x + y = z
if x=1, y=2, z=3 => No
if x=0, y=1, z=1 => yes
not sufficient
stmnt 2. x>0 not sufficient
together,
x=-1, y=5, z=4 =>yes
z=-1, y=-5, z=-6=> yes
(y will always be greater than z)
sufficient, hence C
If you know that x = -a, why do you need to know that x < 0. Lets say the question is |x| = 5
i.e. x = 5 or x = -5
if statement 1 says that x = -5, then why do we need to know that x < 0.
please explain.
i.e. x = 5 or x = -5
if statement 1 says that x = -5, then why do we need to know that x < 0.
please explain.
madhur_ahuja wrote:Lets say question ismehravikas wrote:When you have modulus |x| = a, then x can be
X = +a
Or
X = -a
I’m not sure but the answer should be A. The question can be rephrased as:
X = y – z
OR
X = -y + z
From 1 we do get x = -y + z
madhur_ahuja wrote:Is |x| = y-z ?
1. x + y = z
2. x < 0
Is |x| =a
1. x=-a
2. x <0
Don't you think we both require 1 and 2. Since with 1 only we are proving that x=-a for both x<0 and x>0, which is wrong.
The answer should be C.
In 1st case, x + y = z.
That means, x = -(y-z).
If y is 3, z is 2, then x = -1 and |x| = 1 = (y-z)
If y is 2, z is 3, then x = 1, and |x| = 1 is not equal to (y-z).
so 1st is not sufficient.
In 2nd case, no information about y and z,
so 2nd is not sufficient.
Taking both together, if x is always less than 0, then y should always be greater than z, so in the above example in which y is 3 and z is 2, it will give x = -1, and |x| = 1 = (y-z). So, taking both the conditions together, it is sufficient to answer the question.
In 1st case, x + y = z.
That means, x = -(y-z).
If y is 3, z is 2, then x = -1 and |x| = 1 = (y-z)
If y is 2, z is 3, then x = 1, and |x| = 1 is not equal to (y-z).
so 1st is not sufficient.
In 2nd case, no information about y and z,
so 2nd is not sufficient.
Taking both together, if x is always less than 0, then y should always be greater than z, so in the above example in which y is 3 and z is 2, it will give x = -1, and |x| = 1 = (y-z). So, taking both the conditions together, it is sufficient to answer the question.
X = Y-Z WHEN X>0 OR X = Z-Y WHEN X<0madhur_ahuja wrote:Is |x| = y-z ?
1. x + y = z
2. x < 0
FROM 1
X+Y=Z IE: X = Z-Y , HOWEVER THIS IS ONLY VALID IF X<0...WE DONT KNOW THAT
FROM 2
INSUFF
BOTH ................C
