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Inequalities and Absolute values

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Inequalities and Absolute values

by yankee.musk » Sat May 22, 2010 3:04 pm
Could someone explain with steps for this? I am confused when using Inequalities and Absolute values together

If n < 0 and Square of n < 1/100, then (1/n) must be ?

A. less than -10
B. between -1 and (-1/10)
C. between (-1/10) and 0
D. between 0 and (1/10)
E. greater than 10

Here are the steps that I did:

Given: n < 0 and Square of n < 1/100

(n*n) < (1/100)
Taking Square root gives:
|n| < (1/10)
Since n is negative, the above equation becomes
n > (-1/10)
Taking reciprocal gives,
1/n > (-10) [another question: When taking a reciprocal, would the inequality change?)
....
OA : [spoiler]A[/spoiler]
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by live2win » Sat May 22, 2010 5:29 pm
Here is the simple way to solve

Step 1 : if n < 0 then n must be a negetive number
step 2: square of n < 1/ 100 which means 1/|n| > 10
Step 3: in our case n is a negative number so n should be less than -1/ 10
Step 4: n is less than -10

IMO A

answer to your question, Inequality changes when you take reciprocal
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by liferocks » Sat May 22, 2010 9:03 pm
yankee.musk wrote: Taking reciprocal gives,
1/n > (-10) [another question: When taking a reciprocal, would the inequality change?)
....
OA : A
When taking a reciprocal, would the inequality change?--yes...this is why the step above will give 1/n<-10...ans
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