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NP pg 75 #16

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mobenny
 Post subject: NP pg 75 #16
 Post Posted: Sun Mar 29, 2009 11:01 pm 
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Course Students


Posts: 68
Regarding number properties book and absolute value

Problem #16 pg 75

why is the solution abs value of x+4 and not abs value of x-4?
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JonathanSchneider
 Post subject: Re: NP pg 75 #16
 Post Posted: Wed Apr 01, 2009 5:12 pm 
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ManhattanGMAT Staff


Posts: 480
Location: Durham, NC
There are a number of different ways to think about this.

First, you could just think about the different end points: -7 and -1. When you add 4 to -7, you get -3, which has an absolute value of 3, a match. Ditto for -1. Add 4 to -1 and you get 3, which has an absolute value of 3 as well.

Another way to think about it is that the midpoint of the range is -4. The endpoints extend some amount beyond that. Take a look at pages 112-113 in the EIV book (strategy guide #3) for and explanation of Inequalities and Absolute Value that will allow you to apply these concepts more generally.
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