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What is the value of

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What is the value of

by Max@Math Revolution » Wed Feb 19, 2020 1:07 am
[GMAT math practice question] 2.19

What is the value of \(\sqrt{360x}\) ?

1) x is a 2 digit integer.
2) \(\sqrt{360x}\) is an integer.
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Source: — Data Sufficiency |
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Re: What is the value of

by Max@Math Revolution » Fri Feb 21, 2020 12:35 am
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Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution.
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Since we have 1 variable (x) and 0 equations, D is most likely the answer. So, we should consider each condition on its own first.

Condition 1)

Since we don’t have a unique value from condition 1), it does not yield a unique solution, and it is not sufficient.

Condition 2)

10 and 40 are possible values of x, since \(\sqrt{360\cdot10}=\sqrt{3600}=60\) and \(\sqrt{360\cdot40}=\sqrt{14400}=120\)
Since condition 2) does not yield a unique solution, it is not sufficient.

Conditions 1) & 2)

10 and 40 are possible values of x satisfying both conditions as well.

Since both conditions together do not yield a unique solution, they are not sufficient.

Therefore, E is the answer.
Answer: E

If the original condition includes “1 variable”, or “2 variables and 1 equation”, or “3 variables and 2 equations” etc., one more equation is required to answer the question. If each of conditions 1) and 2) provide an additional equation, there is a 59% chance that D is the answer, a 38% chance that A or B is the answer, and a 3% chance that the answer is C or E. Thus, answer D (conditions 1) and 2), when applied separately, are sufficient to answer the question) is most likely, but there may be cases where the answer is A, B, C, or E.
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