GMAT Prep 2 Practice Test Question 5 Please Help

[kellyeroses]

I searched the forum but couldn't clearly find this question being asked:

If K does not equal 0 or 1 or -1 is 1/K > 0

1 1/k-1>0
2 1/K+1>0

Thanks in advance for your help...

[cris]

I Think is E

[Stuart@KaplanGMAT]

I searched the forum but couldn't clearly find this question being asked:

If K does not equal 0 or 1 or -1 is 1/K > 0

1 1/k-1>0
2 1/K+1>0

Thanks in advance for your help...

For 1/K to be greater than 0, we need K>0 (since that would give us a +/+, which is +, versus a +/-, which is -).

So, as is often the case, you make your life easier by simplifying the question.

If K does not equal 0, 1 or -1, is K > 0?

(1) 1/(k-1) > 0

Again, if we know that the fraction is +, either the numerator and denominator are both + or both -. Since the numerator is +, we know for sure that (k-1) is also +.

So, we know that k - 1 > 0, which means that k > 1. So, back to our original question... Is k > 0? Definitely yes! Statement (1) is sufficient.

(2) 1/(k+1) > 0

Using the same logic as above, we know that k+1 > 0, and therefore (k>-1).

So, back to our original question... Is k > 0? Well, it could be, since it's greater than -1, but it also might not be, since k could = -(1/2). Therefore, statement (2) gives us a sometimes yes and sometimes no answer, which means that it's insufficient.

(1) is sufficient, (2) isn't - choose (A).