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GRE Math Challenge #139-x^2* y < 0
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Updated on: 20 Feb 2020, 16:24
Updated on: 20 Feb 2020, 16:24
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Question Stats:
63% (00:25) correct
36% (00:21) wrong based on 109 sessions
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\((x^2)(y) < 0\)
A)The quantity in Column A is greater.
B)The quantity in Column B is greater.
C)The two quantities are equal.
D)The relationship cannot be determined from the information given.
Kudos for the right answer and explanation
Quantity A |
Quantity B |
\( xy\) |
\(0 \) |
A)The quantity in Column A is greater.
B)The quantity in Column B is greater.
C)The two quantities are equal.
D)The relationship cannot be determined from the information given.
Kudos for the right answer and explanation
Retired Moderator
Joined: 10 Apr 2015
Posts: 6218
Given Kudos: 136
Re: GRE Math Challenge #139
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15 May 2015, 13:52
15 May 2015, 13:52
1
sandy wrote:
\((x^2)(y) < 0\)
Quantity A: xy
Quantity B: 0
Quantity A: xy
Quantity B: 0
Since x^2 is always greater than or equal to zero, and since x^2 does not equal zero (since we're told the expression (x^2)(y) is LESS THAN 0), we can be certain that x^2 is POSITIVE and y is NEGATIVE.
Of course, that x^2 is POSITIVE tells us nothing about whether x itself is positive or negative.
So, x could be positive, or x could be negative.
This brings us to two conflicting cases:
case 1: x = 1 and y = -1
Aside: notice that this satisfies the given inequality (x^2)(y) < 0
In this case we get:
Quantity A: xy = (1)(-1) = -1
Quantity B: 0
Here, quantity B is greater.
case 2: x = -1 and y = -1
Aside: notice that this satisfies the given inequality (x^2)(y) < 0
In this case we get:
Quantity A: xy = (-1)(-1) = 1
Quantity B: 0
Here, quantity A is greater.
Since we can't conclude which quantity is greater, the correct answer is
Show: ::
D
Cheers,
Brent
Re: GRE Math Challenge #139-x^2* y < 0
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11 Aug 2018, 12:54
11 Aug 2018, 12:54
sandy wrote:
\((x^2)(y) < 0\)
Quantity A: xy
Quantity B: 0
• Quantity A is greater.
• Quantity B is greater.
• Both Quantities are Equal
• Cannot be determined
Quantity A: xy
Quantity B: 0
• Quantity A is greater.
• Quantity B is greater.
• Both Quantities are Equal
• Cannot be determined
\(x^2\) is positive but we don't know whether x is positive or negative. Thus we will not get any specific answer.
The best answer is D.
