RR88 wrote:
Bunuel wrote:
10. If n is not equal to 0, is |n| < 4 ?
(1) n^2 > 16
(2) 1/|n| > n
Question basically asks is -4<n<4 true.
(1) n^2>16 --> n>4 or n<-4, the answer to the question is NO. Sufficient.
(2) 1/|n| > n, this is true for all negative values of n, hence we can not answer the question. Not sufficient.
Answer: A.
Hi
Bunuel, thank you so much for such an amazing post, so so so helpful.
A quick query, regarding statement 2 here:
(2) \(\frac{1}{|n|} > n\), Shouldn't it be true for all values of n such that n<1 (n#0) ?
Eg: n =1/2: \(\frac{1}{|(1/2)|} > \frac{1}{2}\) : \(2 > \frac{1}{2}\)
PS: It doesn't alter the final answer though.
Yes, but the fact that it's true for all negative n's was enough to discard this statement. So, we did not need to find the actual range. Still if interested here it is:
\(\frac{1}{| n |}>n\) --> multiply by \(|n|\) (we can safely do that since |n|>0): \(n*|n| < 1\).
If \(n>0\), then we'll have \(n^2<1\) --> \(-1<n<1\). Since we consider the range when \(n>0\), then for this range we'll have \(0<n<1\).
If \(n<0\), then we'll have \(-n^2<1\) --> \(n^2>-1\). Which is true for any n from the range we consider. So, \(n*|n| < 1\) holds true for any negative value of n.
Thus \(\frac{1}{| n |}>n\) holds true if \(n<0\) and \(0<n<1\).