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cubicle_bound_misfit
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ques is n/k=?
stm1. n=(k+1)^3
n^1/3=k+1
n^1/3-k=1 since k>1, this is sufficient
stm2. Insuff
hence A
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If you expand (k+1)^3, you'll see that it's equal to k^3 + 3k^2 + 3k + 1. So,
n = k^3 + 3k^2 + 3k + 1
n = k(k^2 + 3k + 3) + 1
That is, n is one greater than a multiple of k, which means the remainder is 1 when you divide n by k (at least, if k > 1).
In general, I wouldn't have bothered to multiply (k+1)^3 out completely; when you do multiply it out, you may be able to see that every term will have a k in it with the exception of the +1 at the end, and that's all you need to know for this question. So Statement 1) is sufficient, and clearly Statement 2) is not. A.
n = k^3 + 3k^2 + 3k + 1
n = k(k^2 + 3k + 3) + 1
That is, n is one greater than a multiple of k, which means the remainder is 1 when you divide n by k (at least, if k > 1).
In general, I wouldn't have bothered to multiply (k+1)^3 out completely; when you do multiply it out, you may be able to see that every term will have a k in it with the exception of the +1 at the end, and that's all you need to know for this question. So Statement 1) is sufficient, and clearly Statement 2) is not. A.
For online GMAT math tutoring, or to buy my higher-level Quant books and problem sets, contact me at ianstewartgmat at gmail.com
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