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Re: If a = -0.3, which of the following is true?
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10 Jan 2014, 04:32

It's tricky. At first sight I thought hey this is easy, it can only be E. But i re-calculated and saw that -0.3^3 = -0.027 which is bigger than -0.3. So B. Hope I'm as smart in the GMAT and calculate first before picking an answer :D

When using an EVEN power, the negative terms "cancel out", so the result is always positive.

This holds true even when we use a negative power:

(-2)^(-2) = 1/(-2)(-2) = 1/4

The exception I mentioned earlier:

0^2 = (0)(0) = 0 Etc.

GMAT assassins aren't born, they're made, Rich

Thanks. I understood that. But the question says -0.3 and not (-0.3).

-0.3 = -1 * 0.3. Hence, whatever happens, it would be -1 * (0.3)^even number, hence the overall result would still be negative. Read this in the MGMAT Algebra book in the exponents chapter.

Re: If a = -0.3, which of the following is true?
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25 Dec 2015, 12:32

Hi torreadortorment,

You've misinterpreted the question.

Before substituting in the value for 'A', let's look at 'A' to an even power:

A^2 = (A)(A) A^4 = (A)(A)(A)(A) Etc.

NOW, plug in the value for A.... (A = -0.3)....

A^2 = (-0.3)^2 = (-0.3)(-0.3) = +.09 Etc.

IF.... you were given -0.3^2 to start off with, then that calculation WOULD lead you to -.09 (since you have to use PEMDAS rules), but that is NOT what we were given in this question.

Re: If a = -0.3, which of the following is true?
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11 Jun 2016, 06:46

Walkabout wrote:

If a = -0.3, which of the following is true?

(A) a < a^2 < a^3 (B) a < a^3 < a^2 (C) a^2 < a < a^3 (D) a^2 < a^3 < a (E) a^3 < a < a^2

We are given that a = -0.3; what we must keep in mind in this problem is that we are really being tested on what happens when we raise a negative proper fraction to an exponent. We say negative proper fraction because -0.3 = -3/10.

The fact that a = -0.3 is not that important; in fact, we could use any negative proper fraction, such as -1/2 or -1/3 to obtain the correct answer.

Let's look at what happens when a negative proper fraction is raised to an even or odd power.

Rule: When a negative proper fraction is raised to an even-powered or odd-powered exponent, the value increases. If this rule is hard to see, let’s test -1/2. We can start by raising -½ to the even exponent of 2.

(-1/2)^2 =1/4

¼ > -1/2

Clearly, we can see that positive ¼ is greater than -½.

Let’s now check an odd-powered exponent; we can raise -1/2 to an exponent of 3.

(-1/2)^3 = -1/8

-1/8 > -1/2

Although both values are negative, -1/8 is greater than -½.

We can use these rules to answer the question. Since we are raising a negative base to a power, the largest value will be a^2, since that is positive, and a and a^3 are negative. That leaves us with answers B and E. Finally, we know a^3 must be greater than a, thus eliminating answer choice E.

The answer is B.
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GMAT Quant Self-Study Course 500+ lessons 3000+ practice problems 800+ HD solutions

Re: If a = -0.3, which of the following is true?
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13 Jul 2017, 20:38

1

nandetapuri wrote:

Bunuel wrote:

Walkabout wrote:

If a = -0.3, which of the following is true?

(A) a < a^2 < a^3 (B) a < a^3 < a^2 (C) a^2 < a < a^3 (D) a^2 < a^3 < a (E) a^3 < a < a^2

Hello could you please tell me why answer D is incorrect.

D) 0.09 > -0.0027 > -0.3 B) -0.3 < -0.027 < 0.09

Aren't both of them same?

Hi nandetapuri,

It looks like you 'mixed up' the order of the three values. Notice that the largest term in Answer B is "a^2" (which equals +0.09), while the largest term in Answer D is "a" (which equals -0.3). So the answer to your immediate question is NO - Answers B and D are NOT the same.