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If x, y, and r are all nonzero numbers, what is the value of [#permalink]
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30 Aug 2004, 20:30
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This topic is locked. If you want to discuss this question please repost it in the respective forum. If x, y, and r are all nonzero numbers, what is the value of
r = (xy) / (2x+y)
1) lxl = lyl
2) x = 3
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Best Regards,
Paul



Joined: 31 Dec 1969
Location: Russian Federation
Concentration: Entrepreneurship, International Business
GMAT 3: 740 Q40 V50 GMAT 4: 700 Q48 V38 GMAT 5: 710 Q45 V41 GMAT 6: 680 Q47 V36 GMAT 9: 740 Q49 V42 GMAT 11: 500 Q47 V33 GMAT 14: 760 Q49 V44
WE: Supply Chain Management (Energy and Utilities)

My answer [#permalink]
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30 Aug 2004, 21:44
A
Statement 1:x=y OR x=y
if x=y.......r=2
x=y.......r is undefined.........r is a nonzero number.....thus r=2
statement 2....value of y unknown
thus A....what is the OA?



Manager
Joined: 24 Aug 2004
Posts: 66

Stmt 1 alone is suficient.
since r is non zero (mentioned in Ques) hence, x and y, they cannot be both +ve or both ve (as x = y)
so one has to +ve and other ve, so that xy still remains a non zero number, and since their mod values are same, xy = 2x (assuming y = x, there cant be any other valid assumption) and the denominator (2x + y) will be equal to x, so the value of the exp is 2x/x = 2.
stmt 2 alone is obviously not sufficient as there is no way to determine y.



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Joined: 07 Jul 2004
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Location: Singapore

(1) is not sufficient. x can be a negavtive of y, and vice versa. Similarly, both could be similar negative or postive values.
We can try by putting in some numbers, same x = 10, y = 10, then r=2
Or x = 10, y=10, then r = 2
Or x = 10, y=10, then r=0
And x = 10, y=10, then r = 0
So we don't really know the value of r from this statement.
2) Not sufficient as well as we know nothing about y.
(1) and (2), x=3, x=3=y
so y=+3, or 3
If y=+3, x=3, r=33/2(3)+3, and r = 2
If y=3, x=3, r=3+3/2(3)3 and r = 0
So again, we don't really know the value or r.
D should be the answer.
What's the OA?



Joined: 31 Dec 1969
Location: Russian Federation
Concentration: Entrepreneurship, International Business
GMAT 3: 740 Q40 V50 GMAT 4: 700 Q48 V38 GMAT 5: 710 Q45 V41 GMAT 6: 680 Q47 V36 GMAT 9: 740 Q49 V42 GMAT 11: 500 Q47 V33 GMAT 14: 760 Q49 V44
WE: Supply Chain Management (Energy and Utilities)

r is a nonzero number........so statement 1 only gives r=2 n not r =0..........thus statement 1 is enuf to solve the problem
OA plz



Joined: 31 Dec 1969
Location: Russian Federation
Concentration: Entrepreneurship, International Business
GMAT 3: 740 Q40 V50 GMAT 4: 700 Q48 V38 GMAT 5: 710 Q45 V41 GMAT 6: 680 Q47 V36 GMAT 9: 740 Q49 V42 GMAT 11: 500 Q47 V33 GMAT 14: 760 Q49 V44
WE: Supply Chain Management (Energy and Utilities)

r is a nonzero number(see question)........so statement 1 only gives r=2 n not r =0..........thus statement 1 is enuf to solve the problem
OA plz



Manager
Joined: 02 Apr 2004
Posts: 222
Location: Utrecht

I will choose answer A
If I try x = 3 and y = 3, I get r = 6/3
If I try x = 3 and y = 3, I get r = 6/3
Other combinations in 3 are not possible, otherwise r will be zero.
x and y can also be used as other integers or even 1/2
Regards,
Alex



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Joined: 07 Jul 2004
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alex, you forgot to try x=3, y=3, which would give you r=0. You need to try all possible combinatins of the absolute values for x and y.



Manager
Joined: 02 Apr 2004
Posts: 222
Location: Utrecht

But wilfred,
In the question it is specifically mentioned that r, x and y are non zero numbers, so r = 0 is not even of our concern. We need to know the value of r, while we know r is not 0, so r could be of an negative value or positive value. Using x and y as I mentioned all we get is an positive value.
Do you know what I mean?
Regards,
Alex



Senior Manager
Joined: 16 Aug 2004
Posts: 320
Location: India

My answer choice is A.
With A, we have following possibities
(+x,+y) r=0
(x,+y) r=2
(+x,y) r=2
(x,y) r=0
Since r cannot be zero, the value for r=2. therefore sufficient
With B it is not sufficient.
Therefore A



Joined: 31 Dec 1969
Location: Russian Federation
Concentration: Entrepreneurship, International Business
GMAT 3: 740 Q40 V50 GMAT 4: 700 Q48 V38 GMAT 5: 710 Q45 V41 GMAT 6: 680 Q47 V36 GMAT 9: 740 Q49 V42 GMAT 11: 500 Q47 V33 GMAT 14: 760 Q49 V44
WE: Supply Chain Management (Energy and Utilities)

hah ! alex, my bad. I did not spot the limits 'r x and y are nonzero'. No excuses, but i was working that at my workplace, so perhaps I missed it. Great work !



GMAT Club Legend
Joined: 07 Jul 2004
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That 'guest' was me !



SVP
Joined: 16 Oct 2003
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I got it wrong first but yes it should be A.



Manager
Joined: 31 Aug 2004
Posts: 162
Location: Vancouver, BC, Canada

If x, y, and r are all nonzero numbers, what is the value of
r = (xy) / (2x+y)
1) lxl = lyl
2) x = 3
By 1) alone, there are 4 possibilities:
+x, +y or +x, +x
+x, y or +x, x
x, y or x, x
x, +y or x, +x
+x, +y will give (xx) / (2x+x) = 0
+x, y will give (x(x)) / (2xx) = 2x / x = 2
x, y will give (x(x)) / (2xx) = 0 / 3x = 0
x, +y will give (xx) / (2x+x) = 2x / x = 2
Now in the question, it says r cannot be 0, and from the above 4 possibilities, we can eliminate the first and 4th possibilities. This leads us to say r=2, and this allows us to answer the question  what is the value of r if it is a nonzero? We can test by substituting any number into the equation. Let's say x=5 and y=5, we will get r=2. If we let x8, y=8, we will still get r=2. Same apply to x=5, y=5 or x=8, y=8. Why don't we consider x=5, y=5? Because in the question, it says r cannot be 0.
By 2) alone, we have no clue to answer the question.
So my answer is A. Pls post the correct answer....



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Joined: 15 Dec 2003
Posts: 4288

OA is A guys. I thought this was a good catch question where the key lay in the opening sentence r is not equal to 0 so x = y or y = x according to A which is sufficient
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Best Regards,
Paul










