Inequalities

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Inequalities

by pritam.ryders » Wed Aug 21, 2013 11:21 pm
If 4 < 7-x / 3 , which of the following must be true?
1: 5< x
11: |x+3| >2
111: -(x+5) is positive

a) 11: only
b) 111: only
c) 1: and 11:
d) 11: and 111:
e)1:,11: and 111:

Please provide proper explanation
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by macattack » Thu Aug 22, 2013 1:14 am
Rephrase:
(7-x)/3>4
7-x>12
-x>5
x<-5

eliminate 1

choose d
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by GMATGuruNY » Thu Aug 22, 2013 2:45 am
If 4 < (7-x)/3,which of the following must be true?
  • I. 5<x
    2. |x+3|>2
    3. -(x+5) is positive.

    A. II only
    B .III only
    C. I and II only
    D. II and III only
    E. I,II and III
Simplify the expression in the question stem:
4 < (7-x)/3
12 < 7-x
x < -5.
Question stem rephrased:
If x < -5, which of the following must be true?

I: x > 5
Since x is negative, it is not possible that x>5.
Eliminate C and E, which include I.

II: |x+3| > 2.
|x-(-3)| > 2
|x-y| = the DISTANCE between x and y.
Thus, |x-(-3)| > 2 implies the following:
The distance between x and -3 is greater than 2.
Plotted on a number line:
<-----(-5).....(-3).....(-1)----->
The ranges in red are where x is more than 2 places from -3.
Since x<-5, it must be true that the distance between x and -3 will always be greater than 2.
Eliminate B, which does not include II.

III: -(x+5)>0
x+5 < 0
x < -5.
Eliminate A, which does not include III.

The correct answer is D.
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