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11 Jun 2018, 03:15
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B
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Difficulty:
65%
(hard)
Question Stats:
42% (01:05) correct
58%
(01:16)
wrong
based on 64
sessions
History
Date
Time
Result
Not Attempted Yet
If \(w^2 x^3 y^4 z^5 < 0\), is \(xyz > 0\)?
1) \(x < 0\)
2) \(y < 0\)
1) \(x < 0\)
2) \(y < 0\)
11 Jun 2018, 03:15
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Official Solution:
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.
The first step of the VA (Variable Approach) method is to modify the original condition and the question, and then recheck the question.
Modifying the original condition and question:
The original condition \(w^2 x^3 y^4 z^5 < 0\) is equivalent to \(xz < 0\) since we can ignore terms with even exponents in this type of inequality (they are always positive).
Under the modified condition \(xz < 0\), the question, 'is \(xyz > 0\)?' is equivalent to 'is \(y < 0\)?', which is the same as condition 2).
Since condition 1) tells us nothing about the sign of y, the answer is B.
Therefore, the answer is B.
Answer: B
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.
The first step of the VA (Variable Approach) method is to modify the original condition and the question, and then recheck the question.
Modifying the original condition and question:
The original condition \(w^2 x^3 y^4 z^5 < 0\) is equivalent to \(xz < 0\) since we can ignore terms with even exponents in this type of inequality (they are always positive).
Under the modified condition \(xz < 0\), the question, 'is \(xyz > 0\)?' is equivalent to 'is \(y < 0\)?', which is the same as condition 2).
Since condition 1) tells us nothing about the sign of y, the answer is B.
Therefore, the answer is B.
Answer: B
31 Mar 2019, 08:09
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I think this is a high-quality question and I agree with explanation.
