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If r is not equal to 0, is r^2/|r| < 1? (1) r > -1 (2)

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If r is not equal to 0, is r^2/|r| < 1? (1) r > -1 (2)  [#permalink]

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New post 27 Jun 2010, 12:43
2
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A
B
C
D
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Question Stats:

65% (01:35) correct 35% (01:38) wrong based on 486 sessions

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If r is not equal to 0, is r^2/|r| < 1?

(1) r > -1

(2) r < 1

AS far as i know the option B looks sufficient. Since, r<1, it can take values that are negative like -2 or fraction values like
1/2. in either case the value of r^2/ |R| is <1. The OA suggests other wise.

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Re: Mod of R - DS  [#permalink]

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New post 27 Jun 2010, 13:10
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kylexy wrote:
If r is not equal to 0, is r^2/|r| < 1?

(1) r > -1

(2) r < 1

Hi pls help me out with a detailed explanation :lol: :roll:

AS far as i know the option B looks sufficient. Since, r<1, it can take values that are negative like -2 or fraction values like
1/2. in either case the value of r^2/ |R| is <1. The OA suggests other wise.


Is \(\frac{r^2}{|r|}<1\)? --> reduce by \(|r|\) --> is \(|r|<1\)? or is \(-1<r<1\)?

Two statements together give us the sufficient info.

Answer: C.

You made a mistake in calculation for statement (2). Given \(r<1\): for \(-1<r<1\), for example if \(r=-\frac{1}{2}\), then \(\frac{(-\frac{1}{2})^2}{|-\frac{1}{2}|}=\frac{1}{2}<1\) but if \(r\leq{-1}\), for example if \(r=-2\), then \(\frac{(-2)^2}{|-2|}=2>1\).

Hope it's clear.
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Re: Mod of R - DS  [#permalink]

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New post 27 Jun 2010, 13:13
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The first thing to note is that the question isn't testing sign. They tell us that r is not 0, and by definition, both r^2 and |r| are positive. So neither of these statements would be more useful than the other alone.

Since pos/pos = pos, we are ok doing a little creative manipulation of r^2/|r| = |(r*r)/r| = |r|. This move (putting the absolute value sign around the whole thing) isn't a rule to memorize or anything. I'm just ignoring sign temporarily, cancelling, then just assuring the positive result I need with the bars.

This question is really asking "Is r a fraction, or is it larger than 1 (in absolute value)?"
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Re: Mod of R - DS  [#permalink]

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New post 27 Jun 2010, 23:21
C, value of 'r' shall fall in the range -1 and 1 for a single solution to exist.
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Re: Mod of R - DS  [#permalink]

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New post 28 Jun 2010, 02:37
Bunuel wrote:
kylexy wrote:
If r is not equal to 0, is r^2/|r| < 1?

(1) r > -1

(2) r < 1

Hi pls help me out with a detailed explanation :lol: :roll:

AS far as i know the option B looks sufficient. Since, r<1, it can take values that are negative like -2 or fraction values like
1/2. in either case the value of r^2/ |R| is <1. The OA suggests other wise.


Is \(\frac{r^2}{|r|}<1\)? --> reduce by \(|r|\) --> is \(|r|<1\)? or is \(-1<r<1\)?

Two statements together give us the sufficient info.

Answer: C.

You made a mistake in calculation for statement (2). Given \(r<1\): for \(-1<r<1\), for example if \(r=-\frac{1}{2}\), then \(\frac{(-\frac{1}{2})^2}{|-\frac{1}{2}|}=\frac{1}{2}<1\) but if \(r\leq{-1}\), for example if \(r=-2\), then \(\frac{(-2)^2}{|-2|}=2>1\).

Hope it's clear.


I guess i did make a mistake in the calc....my bad!!! thanks for the info bunuel!!!
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Re: If r is not equal to 0, is r^2/|r| < 1? (1) r > -1 (2)  [#permalink]

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New post 18 Aug 2013, 20:48
I just did this question on MGMAT, and learning to use number lines as a tool to answer these questions.

And I got it going well so far. Here is how I did it.

First I simplified the statement, but this is how I did it.

Instead of using long drawn out algebra I made it into 2 conditions.

I made \(\frac{r^2}{|r|} < 1\) into two conditions; first where, both r, and |r| is positive.

Creating the equation r<1, then I took the reverse and said that <-1 creating r>1

Then I took the absolute value into the picture and made it into and created r>1 and r>-1

Which makes it that the answer has to r is between -infinity and positive infinity.

And the only solution that satisfies those conditions is C.

I may have made an error in one of my rationales above but it works
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Re: Mod of R - DS  [#permalink]

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New post 06 Feb 2014, 10:54
Bunuel wrote:
kylexy wrote:
If r is not equal to 0, is r^2/|r| < 1?

(1) r > -1

(2) r < 1

Hi pls help me out with a detailed explanation :lol: :roll:

AS far as i know the option B looks sufficient. Since, r<1, it can take values that are negative like -2 or fraction values like
1/2. in either case the value of r^2/ |R| is <1. The OA suggests other wise.


Is \(\frac{r^2}{|r|}<1\)? -->reduce by \(|r|\) --> is \(|r|<1\)? or is \(-1<r<1\)?

Two statements together give us the sufficient info.

Answer: C.

You made a mistake in calculation for statement (2). Given \(r<1\): for \(-1<r<1\), for example if \(r=-\frac{1}{2}\), then \(\frac{(-\frac{1}{2})^2}{|-\frac{1}{2}|}=\frac{1}{2}<1\) but if \(r\leq{-1}\), for example if \(r=-2\), then \(\frac{(-2)^2}{|-2|}=2>1\).

Hope it's clear.


How r^2/lrl reduce to lrl only ???
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Re: Mod of R - DS  [#permalink]

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New post 07 Feb 2014, 05:29
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sanjoo wrote:
Bunuel wrote:
kylexy wrote:
If r is not equal to 0, is r^2/|r| < 1?

(1) r > -1

(2) r < 1

Hi pls help me out with a detailed explanation :lol: :roll:

AS far as i know the option B looks sufficient. Since, r<1, it can take values that are negative like -2 or fraction values like
1/2. in either case the value of r^2/ |R| is <1. The OA suggests other wise.


Is \(\frac{r^2}{|r|}<1\)? -->reduce by \(|r|\) --> is \(|r|<1\)? or is \(-1<r<1\)?

Two statements together give us the sufficient info.

Answer: C.

You made a mistake in calculation for statement (2). Given \(r<1\): for \(-1<r<1\), for example if \(r=-\frac{1}{2}\), then \(\frac{(-\frac{1}{2})^2}{|-\frac{1}{2}|}=\frac{1}{2}<1\) but if \(r\leq{-1}\), for example if \(r=-2\), then \(\frac{(-2)^2}{|-2|}=2>1\).

Hope it's clear.


How r^2/lrl reduce to lrl only ???


\(r^2=|r|*|r|\) --> \(\frac{r^2}{|r|}\) --> \(\frac{|r|*|r|}{|r|}\) --> \(|r|\).

Hope it's clear.
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Re: If r is not equal to 0, is r^2/|r| < 1? (1) r > -1 (2)  [#permalink]

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New post 06 Nov 2014, 01:36
kylexy wrote:
If r is not equal to 0, is r^2/|r| < 1?

(1) r > -1

(2) r < 1

AS far as i know the option B looks sufficient. Since, r<1, it can take values that are negative like -2 or fraction values like
1/2. in either case the value of r^2/ |R| is <1. The OA suggests other wise.




r^2/|r|<1 ---> r^2<|r|

Logically, the only way when any number squared is less than the same number not squared is when the number is between -1 and 1

S1. r>-1 only one part of interval, so INSUFFICIENT

S2. r<1 again, only one part of interval, INSUFFICIENT

S1+S2 gives full interval, SUFFICIENT

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If r is not equal to 0, is r^2/|r| < 1? (1) r > -1 (2)  [#permalink]

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New post 29 Jan 2017, 03:47
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kylexy wrote:
If r is not equal to 0, is \(\frac{r^{2}}{|r|} < 1\) ?

(1) \(r > -1\)

(2) \(r < 1\)

AS far as i know the option B looks sufficient. Since, \(r<1\), it can take values that are negative like \(-2\) or fraction values like
\(\frac{1}{2}\) . in either case the value of \(\frac{r^2}{|r|}\) is \(<1\). The OA suggests other wise.


Since \(|r|\) is always positive, we can multiply both sides of the inequality by \(|r|\) and rephrase the question as: Is \(r^{2} < |r |\) ? The only way for this to be the case is if \(r\)is a nonzero fraction between \(-1\) and \(1\).
 
(1) INSUFFICIENT: This does not tell us whether \(r\) is between \(-1\) and \(1\). If \(r = - \frac{1}{2}\) , \(|r| = \frac{1}{2}\) and \(r^{2} = \frac{1}{4}\) , and the answer to the rephrased question is YES.  However, if \(r = 4,\) , \(|r| = 4\)and \(r^{2} = 16\), and the answer to the question is NO.

(2) INSUFFICIENT: This does not tell us whether \(r\) is between \(-1\) and \(1\). If \(r = \frac{1}{2}\) , \(|r| = \frac{1}{2}\) ans \(r^{2} = \frac{1}{4}\) , and the answer to the rephrased question is YES.  However, if \(r = -4\), \(|r| = 4\) and \(r^{2}=16\), and the answer to the question is NO.
 
(1) AND (2) SUFFICIENT: Together, the statements tell us that r is between \(-1\) and \(1\). The square of a proper fraction (positive or negative) will always be smaller than the absolute value of that proper fraction.
 
The correct answer is \(C\).
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Re: If r is not equal to 0, is r^2/|r| < 1? (1) r > -1 (2)  [#permalink]

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Re: If r is not equal to 0, is r^2/|r| < 1? (1) r > -1 (2)   [#permalink] 16 Apr 2019, 16:25
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