Inequality

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tapanmittal: Senior | Next Rank: 100 Posts; Posts: 31; Joined: Fri Apr 10, 2015 4:04 am

by tapanmittal » Tue Aug 25, 2015 7:12 pm

If x^3 < 16x, which of the following includes at least some of the possible solutions for x, but no
values that are not solutions?
(A) |x| < 4
(B) x < 4
(C) x > 4
(D) x < -4
(E) x > 0

OA D

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Source: Beat The GMAT — Problem Solving | Tue Aug 25, 2015 7:12 pm

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by [email protected] » Tue Aug 25, 2015 8:40 pm

Hi tapanmittal,

This question can be solved by TESTing VALUES and eliminating answer choices. Notice how the answers all seem to 'revolve around the numbers 4 and -4.....

We're told that X^3 < 16X. We're told to find an answer that does NOT include any non-solutions for X...If you TEST VALUES, you should be able to eliminate some of the Answers...

X=0
0 is NOT < 0, so 0 is NOT a solution
Eliminate Answers A and B.

X=5
125 is NOT < 80, so 5 is NOT a solution
Eliminate Answers C and E

There's only one answer remaining...

Final Answer: D

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

Contact Rich at [email protected]

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bubbliiiiiiii: Legendary Member; Posts: 979; Joined: Tue Apr 14, 2009 1:38 amFollowed by: 12 members; Location: Hyderabad, India; Thanked: 49 times; GMAT Score:700

by bubbliiiiiiii » Tue Aug 25, 2015 10:36 pm

x(x2 - 16) < 0

=> x < 0, x < 4 and x < -4

D satisfies all three.

Regards,

Pranay

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