Princeton Review 1012 pg 137 #7 - book error?

Question

I'm having trouble with this question and was looking for some guidance.

7) Is 1/m 1/1 -1/2 I don't think 1) is sufficient by itself.

Repeat the process for 2). it is a yes for 2 and 10. It is a no for -5 and -2.

If you did a system and substituted m=3+n and m=3n-2. Then 3n-2=3+n. => 5=2n. N=2.5, then m must be 5.5.

On page 190, Princeton Review says the answer is A. Can you all confirm?

gmat1220 · Answer

You dont have to combine.

Statement 1) tells us that m is greater than n. If you remove 3 from the right then we can say

m > n

That's what we need to get a certain answer. The answer is YES

Statement 2) is insufficient.

Lets see some values - 3n=m+2

m = 1, n = 1 The answer is NO
m = 4, n = 2 The answer is YES
m = -8, n = -2 The answer is NO

Hence the answer can be YES or NO

Pique · Answer

I thought that for all numbers you created that met the criteria given, the answer has to always be the same in order for the answer to be sufficient. I understand logically what you're saying, but in practice the -2 provides an exception. As you said, M>N, just as 1>-2, right?

amit2k9 · Answer

check for positive and negative sides.

m,n = 4,1| -2,-5

for a both results are same. Hence sufficient.

for b both results are different.Hence not sufficient.

A.

fluke · Answer

Try with these two sets:

m=1; n=-2
m=5; n=2

A alone not sufficient.

IanStewart · Answer

I'm having trouble with this question and was looking for some guidance.

7) Is 1/m n. It is certainly then possible then that m is positive and n is negative, in which case the answer to the question is clearly 'no' (since 1/m would be positive and 1/n would be negative). But if m and n are both positive, we can divide by mn on both sides of the inequality m > n to see that 1/n > 1/m, in which case the answer is 'yes'.

Statement 2 alone is not the kind of information that is likely to be sufficient, since you cannot even tell which of m or n is larger. As you've done above, you can generate examples that establish Statement 2 is not sufficient. If, say, m=n=1, the answer to the question is 'no', and if m=4 and n=2 the answer is 'yes'.

Combining the two statements, we have two distinct linear equations in two unknowns, so we can certainly solve for m and n and therefore answer any question at all, so the answer is C.

Princeton Review 1012 pg 137 #7 - book error?

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