Is n > 6?

[curtisyasutake]

Is n > 6?

1) sqrt(n) > 2.5
2) n > sqrt(37)

OA is D. I was thinking the answer should be A because n > 6 or n < -6 and n > sqrt(37) would still be true, thus we don't know if n > 6. Please help.

[tim]

i can't actually follow your reasoning. can you explain again what you did?

[curtisyasutake]

Sorry, it seems to me that 2) should be insufficient. If n > sqrt(37), isn't n > 6 or n < -6? If this is the case, we can't tell from 2) whether n > 6 or not.

[dobhal.mayank]

Sorry, it seems to me that 2) should be insufficient. If n > sqrt(37), isn't n > 6 or n < -6? If this is the case, we can't tell from 2) whether n > 6 or not.

Your reasoning seems to be correct. Not quite sure of the OA

[tim]

wrong. you need to review the rules about multiple solutions and when you need both a positive and negative solution. don't just arbitrarily make up a negative solution when it doesn't belong, as in this case. ask yourself what mathematical operation you performed and you should see that there is no justification for the negative "solution" here..

[amycompton]

Is n > 6?

1) sqrt(n) > 2.5
2) n > sqrt(37)

What is the value of 'n' ?

If assuming n=3

n>6 is yes
Also the above condition satisfied
1- True condition
2- True condition

[tim]

Amy, assuming n=3 is definitely not the way you want to approach this one. Please review the rules for how to solve data sufficiency problems, and try this one again using proper techniques..

[curtisyasutake]

Tim,

Would you be willing to explain some of the mathematical justification for why my approach does not work? I squared both sides of n > sqrt(37) to arrive at n^2 > 37. In this case, n could be > 6 or n < -6. This is how I arrived at both a positive and negative solution for n. Why is this not allowed?

I'm taking the GMAT tomorrow, so an expedited response would be much appreciated! Thanks.

[curtisyasutake]

Nevermind, I figured out. I was overthinking this...

[nikhil.baveja]

Is n > 6?

1) sqrt(n) > 2.5
2) n > sqrt(37)

OA is D. I was thinking the answer should be A because n > 6 or n < -6 and n > sqrt(37) would still be true, thus we don't know if n > 6. Please help.

The Logic is Sqrt can never hold a -tive number atleast in GMAT.
so Sqrt-2.5 * Sqrt-2.5 is not possible, it has to be Sqrt2.5*sqrt2.5.

[tim]

let us know if anyone has further questions on this one..

[kuhlmann.b]

I still don't get why 2 is sufficient. There is nothing in the question that would restrict N from being a negative value. Can you explain why N can't be negative for 2)?

[tim]

By definition, the square root function is a non-negative function. In other words, if the GMAT ever draws a square root sign on the page, it means only the non-negative value. As such, if n is greater than a square root, it must be positive.