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0% (00:00) correct
 0% (00:00) wrong based on 0 sessions
DS -
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GMAT Club Legend
Joined: 07 Jul 2004
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1) m^2 : 1 = 7:5 does not tells us anything about n. So (1) is not sufficient.
2) m^2:n = 7:5, so we can write, m^2/n = 7/5, 5m^2 = 7n, n = 5m^2/7
Substituting to m/n^2 = (m)/(5m^2/7) does not solve our problem, as we will still get a ratio that is in the form of m
Using (1) and (2), we know n = 1, so we can find m and solve m/n^2.
(C) is the answer
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Manager
Joined: 02 Apr 2004
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I think the answer is B
M^2/N = 7/5 ==> sqrt 7 * sgrt 7 / 5
M/N^2 = sgrt 7/5^2
Correct me if I am wrong.
Regards,
Alex
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Senior Manager
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My answer choice is E.
A is insufficient asit just says m^2=7/5
B is also insufficient as m^2/n=7/5
This rules out D option as well
From A m=+ or - sqrt 7/5
Using A and B n=1
But we need to find m/n^2. We don't know if it is +7/5 or -7/5.
Hence E
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The answer given is C and even i got E ( explanation similar to dushver's).
Alex_NL, we cant say that if m^2/n = 7/5, then m/n^2 = sqrt7/25.
We can prove this by plugging some values.
m=6,n=8.
m^2/n=36/8=9/2
m/n^2=6/64 (actual value)
m/n^2 (per your method) = 3/4.
these two are not equal.
Thanks.
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Anuramm,
You are right.
I realized that last night, but did not have the energy to correct myself.
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GMAT Club Legend
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It can't be E because if you use both equation, you can tell that n is actually 1. See my working above.
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GMAT Club Legend
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If mn!=0, what is the ratio of m to n^2?
1. The ratio of m^2 to 1 is 7/5
2. The ratio of m^2 to n is 7/5
From 1, nothing is said about n, so it is insufficient.
From 2, it can be written as m^2/n = 7/5, 5m^2 = 7n, n = (5m^2)/7
So using this, m/n^2 = 7m/25m^4 = 7/25m^3. Still we can’t figure out what the ratio is.
Using 1 and 2, we can see that n is actually 1, so with this in hand, we can get 5m^2=7n,
5m^2=7, m = sqrt(7/5). So m:n^2 = sqrt(7/5): 1. Sufficient.
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