Data Sufficiency

Max@Math Revolution wrote:Is (r³)(x) > 0?

1) r� = 1
2) x > 0

Target question: Is (r³)(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