Is (r^2)x>0?
1) r^5=1
2) x>0
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Is (r^2)x>0?
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- Max@Math Revolution
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- Max@Math Revolution
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There are two variables (r and x) in the original condition. In order to match the number of variables and the number of equations, we need 2 equations. Hence, the correct answer is C.
- Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.
- Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.
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- Brent@GMATPrepNow
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Target question: Is (r³)(x) > 0?Max@Math Revolution wrote:Is (r³)(x) > 0?
1) r� = 1
2) x > 0
Statement 1: r� = 1
This tells us that r = 1, however we don't know the value of x.
Let's TEST some values.
Case a: r = 1 and x = 1, in which case (r³)(x) = (1³)(1) = 1. Here, (r³)(x) > 0
Case b: r = 1 and x = -1, in which case (r³)(x) = (1³)(-1) = -1. Here, (r³)(x) < 0
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT
Statement 2: x > 0
Okay, x is POSITIVE, however we don't know the value of r.
Let's TEST some values.
Case a: r = 1 and x = 1, in which case (r³)(x) = (1³)(1) = 1. Here, (r³)(x) > 0
Case b: r = -1 and x = 1, in which case (r³)(x) = (-1)³(1) = -1. Here, (r³)(x) < 0
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT
Statements 1 and 2 combined
Statement 1 tells us that r = 1, which means r³ = 1
Statement 2 tells us that x is POSITIVE
This means that (r³)(x) = (1³)(POSITIVE) = SOME POSITVE #. In other words, (r³)(x) > 0
Since we can answer the target question with certainty, the combined statements are SUFFICIENT
Answer = C
Cheers,
Brent