Bunuel wrote:

Is x a negative number?

(1) 9x > 10x

(2) x + 3 is positive.

Solution:

We need to determine whether x is a negative number.

Statement One Alone:9x > 10x

We can subtract 9x from both sides of the inequality:

9x – 9x > 10x – 9x

0 > x

Since 0 is greater than x, x is less than 0. In other words, x must be negative.

Statement one alone is sufficient to answer the question. We can eliminate answer choices B, C and E.

Statement Two Alone:x + 3 is positive.

From statement two we see that x itself could be either positive or negative. Let’s use a few convenient values to illustrate.

If x is positive

Let x = 1:

1 + 3 = 4, which is positive.

If x is negative

Let x = -1:

-1 + 3 = 2, which is also positive.

Statement two alone is not sufficient to answer the question.

The answer is A.

_________________

Jeffery Miller

Head of GMAT Instruction

GMAT Quant Self-Study Course

500+ lessons 3000+ practice problems 800+ HD solutions