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GPrep question

by gmataug08 » Sat Sep 13, 2008 9:58 am
If x is an negative integer, which of the following expressions has the LEAST value?

(A) x^2 - 0.50
(B) x^2 - 0.51
(C) x^3 - 0.502
(D) x^3 - 0.511
(E) x^4 - 0.512


the answer I selected was C . But the correct answer is D it seems. Can someone explain how .... TIA :)
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Re: GPrep question

by parallel_chase » Sat Sep 13, 2008 10:06 am
gmataug08 wrote:If x is an negative integer, which of the following expressions has the LEAST value?

(A) x^2 - 0.50
(B) x^2 - 0.51
(C) x^3 - 0.502
(D) x^3 - 0.511
(E) x^4 - 0.512


the answer I selected was C . But the correct answer is D it seems. Can someone explain how .... TIA :)
when x is negative, the least value of expression will be when x is subtracted by largest value.

You can easily eliminate options with positive exponents.

Therefore you are left with C and D.

out of C and D only D is being subtracted by larger value therefore it will have the least value.

You also try and pluggin -1 as x to find which number is least

-1 - 0.502 = -1.502

-1 - 0.511 = -1.511

Therefore D is the answer.
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Re: GPrep question

by gmataug08 » Sat Sep 13, 2008 10:32 am
parallel_chase wrote:
gmataug08 wrote:If x is an negative integer, which of the following expressions has the LEAST value?

(A) x^2 - 0.50
(B) x^2 - 0.51
(C) x^3 - 0.502
(D) x^3 - 0.511
(E) x^4 - 0.512


the answer I selected was C . But the correct answer is D it seems. Can someone explain how .... TIA :)
when x is negative, the least value of expression will be when x is subtracted by largest value.

You can easily eliminate options with positive exponents.

Therefore you are left with C and D.

out of C and D only D is being subtracted by larger value therefore it will have the least value.

You also try and pluggin -1 as x to find which number is least

-1 - 0.502 = -1.502

-1 - 0.511 = -1.511

Therefore D is the answer.
Thanks for the explanation.

I got down till...... option between -1.502 & -1.511 . then concluded that -1.502 is less than -1.511 . Now it strikes that , as it is negative value, the farther from 0 the lesser value. It didn't while I took the test :(
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by maf1234 » Thu Jan 29, 2015 5:40 am
I still do not understand the answer.. please can someone help?
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by GMATinsight » Thu Jan 29, 2015 5:50 am
maf1234 wrote:I still do not understand the answer.. please can someone help?
Question: If x is an negative integer, which of the following expressions has the LEAST value?

(A) x^2 - 0.50
(B) x^2 - 0.51
(C) x^3 - 0.502
(D) x^3 - 0.511
(E) x^4 - 0.512

Since we have to find out the LEAST of given option then we start from the Information Given

Step 1) x is Negative and x is Integer
Step 2) Understand the any Negative number to the power EVEN will result in positive value and any Negative number to the power ODD will result in Negative value

Therefore we can remove Options A, B and E as x^2 or x^4 will be positive whereas x^3 will be negative and thus will render a Lesser value than value in Options A, B and E

Step 3) Remaining Options C and D have x^3 common and the difference lies between the part being subtracted i.e. 0.502 and 0.511

Now Understand that a bigger number subtracted will render the lesser value therefore x^3 - 0.511 will be a lesser value

Answer: Option D
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by DavidG@VeritasPrep » Thu Jan 29, 2015 5:51 am
Think about it this way: if we want the smallest possible value, we want the value that is farthest to the left on the number line. (Imagine the number line: -2 is smaller than -1. The more negative we get, the farther to the left we go.)

Right off the bat, we can eliminate the answer choices that are raised to an even exponent. Any negative raised to an even will become positive. (Any negative raised to an odd will remain negative.) We want the smallest value, so we want an answer where x is raised to an odd. A, B, and E are out.

Now we choose between C and D. Well, in D we're subtracting .511 and in C we're subtracting .502. If we want the SMALLEST value, we want to be subtracting as much as possible. In D we subtract more, so that must be the smallest value.

The answer, then is D.
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by [email protected] » Thu Jan 29, 2015 10:58 am
Hi maf1234,

The explanations in this thread have focused on the Number Properties involved; these are important rules to know, since the GMAT Tests them repeatedly.

There's also a practical way to get to the correct answer. The question tells us that X is NEGATIVE INTEGER and we're asked which of the 5 answers has the LEAST VALUE. It doesn't ask "which COULD have the least value", it asks "which...HAS.....the least value." So, one of these answer will ALWAYS be smallest whenever X is a NEGATIVE INTEGER. We can TEST VALUES and prove which is smallest.

IF...
X = -2

A: 4 - 0.50 = +3.5
B: 4 - 0.51 = +3.49
C: -8 - 0.502 = -8.502
D: -8 - 0.511 = -8.511
E: 16 - 0.512 = +15.488

Answer D is "farther left" on a number line, so it is smaller than Answer C (all of the other answers are positive).

Final Answer: D

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