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Even if n was a fraction, wouldnt sqrt(n) still lie between 7 and 8 if we take both the statements together? Yurik79 could you elaborate? I mean if n was 55.5 then sqrt(55.5) would still be between 7 and 8 right? Am I missing something here?

Even if n was a fraction, wouldnt sqrt(n) still lie between 7 and 8 if we take both the statements together? Yurik79 could you elaborate? I mean if n was 55.5 then sqrt(55.5) would still be between 7 and 8 right? Am I missing something here?

No, you are not missing anything
Even if we consider fractions between 7 & 8, "C" holds good!

Guys, please explain me. What if n = 49.5? sqrt(n) will still be between 7 and 8. So, shouldn't the domain of n be (49,64) exluding 49 and 64?

chuckle,
The question asks whether, 7 < sqrt(n) < 8? given that n>50 & n < 60.
From the given two conditions it lies between that range.

You are right, sqrt(49.5) will still lie between 7 & 8 (it is 7.02..) but that is not what this DS asks, it just wants us to tell,
if n>50 & n < 60, is 7 < sqrt(n) < 8 true?

I will also go with E as
a) n > 50 - obviously insufficient
b) n < 60 - obviously insufficient
a & b) for every n (where 50 < n < 60), sqrt(n) is either +ve or -ve - so insufficient.

On the GMAT , the sqrt is always positive. sqrt(4) is always 2 and not -2.
In my opinion, that is $@#%$%$%, but we need to keep that in mind for such problems.

Professor wrote:

hellom3p wrote:

gmat_crack wrote:

hellom3p wrote:

what about -8<sqrt (n)<-7? 49<n<64

Question is not asking for -ve values.

why not? it's like asking: Is sqrt(n) negative? I. n = 49 II. n = 64

E seems correct to me cuz even if 49<n<64, sqrt(n) can be +ve and -ve. so sqrt can or canot fall between 7 and 8.

On the GMAT , the sqrt is always positive. sqrt(4) is always 2 and not -2. In my opinion, that is $@#%$%$%, but we need to keep that in mind for such problems.

Oh! I did not know about this at all. Any ways can you please tell me is this a general thumb rule for all DS questions or it applies to the whole quantitative section? _________________