Is x > y ?

[amitansu]

Is x > y ?

1. [x] - absolute value of x = -8

2. y/absolute value of x = 1/2

[Stuart@KaplanGMAT]

Is x > y ?

1. [x] - absolute value of x = -8

2. y/absolute value of x = 1/2

I'm going to assume that [x] is just x.

(1) clearly insufficient, says nothing about y

(2) since y/|x| is positive, we know that y and |x| are the same sign. Since |x| is always positive, y must be positive.

However, x itself could be positive or negative. So, we could pick:

y = 1 and x = 2. Is 2 > 1? yes

y = 1 and x = -2. Is -2 > 1? no

Insufficient.

Now that we're combining, let's actually think about (1).

(1) x - |x| = -8

Let's rewrite as:

x + 8 = |x|

If x is positive, we'd get:

x + 8 = x (or 8 = 0), which of course is impossible. Therefore, x must be negative.

Do we care what the value is? No!

From statement (2) we know that y is definitely positive. So, if y is positive and x is negative, we know that the answer to "is x > y" is DEFINITELY NOT.

Together, statements (1) and (2) are sufficient: choose (c).

[amitansu]

My choice was also c.
However i was a bit confused by the term [x].

So was confusing between c and e.

Does [x] has got any more interpretation other than just being 'x' in mathematics ?

Btw thanks, for your help ,Stuart.

[maihuna]

any idea abt the source of this Q?

[gmat740]

I'm going to assume that [x] is just x.

Does [x] has got any more interpretation other than just being 'x' in mathematics ?

[x] is a step function in Calculus

[] means the greatest integer term.

eg : [8.3] = 8

[] this function rounds up the number to its nearest integer(the integer has to be smaller or equal to the original number)

eg : [-9.2] = -10

Hope this helps

Karan

[rohitd80]

Hi Kevin,
I've been struggling with similar DS questions this past week. I would appreciate if you can point me to some direction where I could solidify my fundamentals.

Re Statement [2] you explained:
(2) since y/|x| is positive, we know that y and |x| are the same sign. Since |x| is always positive, y must be positive.

However, x itself could be positive or negative. So, we could pick:

y = 1 and x = 2. Is 2 > 1? yes

y = 1 and x = -2. Is -2 > 1? no

Insufficient.

You are approaching this statement with the notion that albeit y/|x| is positive but x can actually be either +ve or -ve....which makes absolute sense!

Recently, I came across a similar question
If x ≠0, then what is the value of |x|/x?

(1) sqrt(x^2) = x
(2) |x−4|=x/3

My approach on condition 1) sqrt(x^2) = x
For +ve value of x...solving the condition will yield a +ve value of x
And, for a -ve value of x...solving the condition will still yield a +ve value of x
So I took the statement as a hint or guide! and said that x could still be -ve in value:
for +ve x --> |x|/x = 1
for -ve x --> |x|/x = -1
So we can't say whether |x|/x is +ve or -ve. Therefore. the condition/statement 1) is insufficient.

Are we supposed to treat these statements as absolute truth or just a hint/guiding statement?

[j_shreyans]

Hi ,

I didn't get the solution , please explain the answer.

Thanks,

Shreyans

[GMATGuruNY]

Is x > y ?

1. x - |x| = -8

2. y/|x| = 1/2

Statement 1: x - |x| = -8
No information about y.
INSUFFICIENT.

Statement 2: y/|x| = 1/2
If y=1 and x=2, then x>y.
If y=1 and x=-2, then x<y.
INSUFFICIENT.

Statements combine:.
Statement 1 implies the following:
x + 8 = |x|.

Case 1: Signs unchanged
x + 8 = x
8 = 0.
Not possible.

Case 2: Signs changed in the absolute value
x + 8 = -x
2x = -8
x = -4.

Since x=-4 and y/|x| = 1/2, we get:
y/|-4| = 1/2
y/4 = 1/2
y = 2.
Thus, x < y.
SUFFICIENT.

The correct answer is C.