Hello again! I'm back with another Data Sufficiency question as part of the contest (see main page) in which David, Ashley and I are posting original questions with prizes for the first few correct answers - and remember to show your work! Here goes, and I apologize for the linear fraction format in statement one...
What is the value of x + y?
1) [4x^2 - 4y^2]/[2(x+y)] = 2x - 2y
2) 3x + 2y = 24
Veritas Prep Challenge Question - DS#3
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What is the value of x + y?
1) [4x^2 - 4y^2]/[2(x+y)] = 2x - 2y
2) 3x + 2y = 24
Considering Statement 1
4 (x^2 - y^2 )/ 2 (x+y) = 2 (x-y)
cross multiplying denominator of Left hand side to Right Hand Side
(x^2 - y^2 ) = (x-y)(x-y)
x2-y2=x2-y2
so this gives us little info about the value of x + y
Statement 2 also doesnt let us know anything about the value of x + y on its own
Even if we combine (1) and (2)
we are not able to know the value .
So Answer is E
1) [4x^2 - 4y^2]/[2(x+y)] = 2x - 2y
2) 3x + 2y = 24
Considering Statement 1
4 (x^2 - y^2 )/ 2 (x+y) = 2 (x-y)
cross multiplying denominator of Left hand side to Right Hand Side
(x^2 - y^2 ) = (x-y)(x-y)
x2-y2=x2-y2
so this gives us little info about the value of x + y
Statement 2 also doesnt let us know anything about the value of x + y on its own
Even if we combine (1) and (2)
we are not able to know the value .
So Answer is E
I Seek Explanations Not Answers
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Hi,
From(1):
4(x+y)(x-y)/2(x+y) = 2(x-y). This is true for all x, y provided x+y is not equal to zero.
There can be many values for (x+y).
Not sufficient to find unique value of (x+y)
From(2):
3x+2y = 24
x=8, y=0
x=0, y=12
Infinitely many values of x and y satisfy this equation.
We cannot find unique (x+y) from this equation
Not sufficient
Both(1) and (2):
x+y not equal to zero and 3x+2y = 24
Not sufficient
Hence, E
From(1):
4(x+y)(x-y)/2(x+y) = 2(x-y). This is true for all x, y provided x+y is not equal to zero.
There can be many values for (x+y).
Not sufficient to find unique value of (x+y)
From(2):
3x+2y = 24
x=8, y=0
x=0, y=12
Infinitely many values of x and y satisfy this equation.
We cannot find unique (x+y) from this equation
Not sufficient
Both(1) and (2):
x+y not equal to zero and 3x+2y = 24
Not sufficient
Hence, E
Cheers!
Things are not what they appear to be... nor are they otherwise
Things are not what they appear to be... nor are they otherwise
For this
Statement 1 is insufficient
[4x^2 - 4y^2]/[2(x+y)] = 2x - 2y (as a^2 - b^2 = (a+b)(a-b))
therefore, 2x - 2y = 2x -2y, which is true but there is no value for x and y. Hence x+y cannot be determined.
Statement 2 is also insufficient
as it gives the value of 3x+2y=24, but individually we wont be able to calculate x or y
Combining the two statements also yields no solution as statement 1 is an incarnation of a formula and statement 2 not to the point.
Hence the Answer is E
Statement 1 is insufficient
[4x^2 - 4y^2]/[2(x+y)] = 2x - 2y (as a^2 - b^2 = (a+b)(a-b))
therefore, 2x - 2y = 2x -2y, which is true but there is no value for x and y. Hence x+y cannot be determined.
Statement 2 is also insufficient
as it gives the value of 3x+2y=24, but individually we wont be able to calculate x or y
Combining the two statements also yields no solution as statement 1 is an incarnation of a formula and statement 2 not to the point.
Hence the Answer is E
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I know i got it right when my answer matched yoursFrankenstein wrote:Hi,
From(1):
4(x+y)(x-y)/2(x+y) = 2(x-y). This is true for all x, y provided x+y is not equal to zero.
There can be many values for (x+y).
Not sufficient to find unique value of (x+y)
From(2):
3x+2y = 24
x=8, y=0
x=0, y=12
Infinitely many values of x and y satisfy this equation.
We cannot find unique (x+y) from this equation
Not sufficient
Both(1) and (2):
x+y not equal to zero and 3x+2y = 24
Not sufficient
Hence, E
I Seek Explanations Not Answers
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I hope I don't disappoint youmundasingh123 wrote:I know i got it right when my answer matched yours
Cheers!
Things are not what they appear to be... nor are they otherwise
Things are not what they appear to be... nor are they otherwise
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Man , You can be sure i wouldnt like itFrankenstein wrote:I hope I don't disappoint youmundasingh123 wrote:I know i got it right when my answer matched yours
I Seek Explanations Not Answers
- abhimanyu.tanwar
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Considering condition (1)
1) [4x^2 - 4y^2]/[2(x+y)] = 2x - 2y
LHS = [4(x^2 - y^2)]/[2(x+y)]
= [4(x-y)(x+y)]/[2(x+y)]
=2x - 2y
=RHS
This does not get us the answer.
Considering condition (2)
2) 3x + 2y = 24
=> x + 2 (x+y) = 24
This also does not get us the value of x+y.
and combining both the conditions also doesnt get us the value of x+y.
Since we cant get the value of (x+y) through both the conditions 1 and 2 considering them simultaneous hence E is the CORRECT ANSWER.
1) [4x^2 - 4y^2]/[2(x+y)] = 2x - 2y
LHS = [4(x^2 - y^2)]/[2(x+y)]
= [4(x-y)(x+y)]/[2(x+y)]
=2x - 2y
=RHS
This does not get us the answer.
Considering condition (2)
2) 3x + 2y = 24
=> x + 2 (x+y) = 24
This also does not get us the value of x+y.
and combining both the conditions also doesnt get us the value of x+y.
Since we cant get the value of (x+y) through both the conditions 1 and 2 considering them simultaneous hence E is the CORRECT ANSWER.
Regards
Abhimanyu
Abhimanyu
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What is the value of x + y?
1) [4x^2 - 4y^2]/[2(x+y)] = 2x - 2y
2) 3x + 2y = 24
Statement 1 reduces to 2x-2y = 2x-2y once we factorise LHS as 2*(x+y)*2*(x-y)/2(x+y), so we cant determine value of x+y
Statement 2 is an equation that cannot be simplified further and hence cant be used to determine the value of x+y
Even after combining information from both the statements, we cannot get value of x+y, hence Statement 1 and statement 2 are not enough so answer is E
1) [4x^2 - 4y^2]/[2(x+y)] = 2x - 2y
2) 3x + 2y = 24
Statement 1 reduces to 2x-2y = 2x-2y once we factorise LHS as 2*(x+y)*2*(x-y)/2(x+y), so we cant determine value of x+y
Statement 2 is an equation that cannot be simplified further and hence cant be used to determine the value of x+y
Even after combining information from both the statements, we cannot get value of x+y, hence Statement 1 and statement 2 are not enough so answer is E
Last edited by ttin0307 on Fri Jul 08, 2011 8:58 am, edited 1 time in total.
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Great work, everyone - the correct answer is, indeed, E.
Statement 1 factors out so that the numerator becomes (2x + 2y)(2x - 2y), allowing the left hand parentheses to factor with the denominator (both are 2x + 2y), leaving just:
2x - 2y = 2x - 2y
That has infinite solutions, so statement 1 doesn't really say anything at all.
Statement 2 has multiple solutions, as well; it's not horrendously far away from being sufficient (if the coefficients for 3x and 2y were the same, say 2x + 2y = 24, we could solve for x+y) and might convince test-takers that you could do something with it, but as there are indeed multiple solutions (x = 8, y = 0; or y = 12, x = 0, for example) the statement is not sufficient.
And since statement 1 really said nothing at all, there's no hope for using both together, so the correct answer is E.
What I like about this question is that the GMAT can be pretty crafty with statements that may look informational but, when taken a step or two from their given form, can actually add a lot less value than you'd think. If it looks pretty easy to get answer choice C, be very careful - more often than not either one statement is good enough on its own, or as in this case one of the statements may not give you the information you think it does.
E isn't a correct answer choice the GMAT likes to give out lightly - when it's correct you usually have to work to prove it, as in this case.
Statement 1 factors out so that the numerator becomes (2x + 2y)(2x - 2y), allowing the left hand parentheses to factor with the denominator (both are 2x + 2y), leaving just:
2x - 2y = 2x - 2y
That has infinite solutions, so statement 1 doesn't really say anything at all.
Statement 2 has multiple solutions, as well; it's not horrendously far away from being sufficient (if the coefficients for 3x and 2y were the same, say 2x + 2y = 24, we could solve for x+y) and might convince test-takers that you could do something with it, but as there are indeed multiple solutions (x = 8, y = 0; or y = 12, x = 0, for example) the statement is not sufficient.
And since statement 1 really said nothing at all, there's no hope for using both together, so the correct answer is E.
What I like about this question is that the GMAT can be pretty crafty with statements that may look informational but, when taken a step or two from their given form, can actually add a lot less value than you'd think. If it looks pretty easy to get answer choice C, be very careful - more often than not either one statement is good enough on its own, or as in this case one of the statements may not give you the information you think it does.
E isn't a correct answer choice the GMAT likes to give out lightly - when it's correct you usually have to work to prove it, as in this case.
Brian Galvin
GMAT Instructor
Chief Academic Officer
Veritas Prep
Looking for GMAT practice questions? Try out the Veritas Prep Question Bank. Learn More.
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- amit2k9
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a comes out to x-y = x-y. hence infinite solutions for x and y. not sufficient.
b x and y may or may not be integers. hence many solution. not sufficient.
a+b many solutions. not sufficient.
E it is.
b x and y may or may not be integers. hence many solution. not sufficient.
a+b many solutions. not sufficient.
E it is.
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