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If 0.010<x-√5<0.011, approximation of 1/√5-1/x is which of the followi

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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 6390
GMAT 1: 760 Q51 V42
GPA: 3.82
If 0.010<x-√5<0.011, approximation of 1/√5-1/x is which of the followi  [#permalink]

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17 Oct 2017, 03:27
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Difficulty:

65% (hard)

Question Stats:

57% (02:22) correct 43% (02:36) wrong based on 76 sessions

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[GMAT math practice question]

If 0.010<x-√5<0.011, approximation of 1/√5-1/x is which of the following options?

A. 0.01
B. 0.002
C. 0.02
D. 0.003
E. 0.03

_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
"Only $99 for 3 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself" Math Expert Joined: 02 Aug 2009 Posts: 6971 Re: If 0.010<x-√5<0.011, approximation of 1/√5-1/x is which of the followi [#permalink] Show Tags 17 Oct 2017, 08:03 MathRevolution wrote: [GMAT math practice question] If 0.010<x-√5<0.011, approximation of 1/√5-1/x is which of the following options? A. 0.01 B. 0.002 C. 0.02 D. 0.003 E. 0.03 0.010<x-√5<0.011........ basically means x-√5~0....x~√5... Let's see the equation now.. $$\frac{1}{√5}-\frac{1}{x}=\frac{x-√5}{x√5}=\frac{0.010}{√5*√5}=0.002$$ B _________________ 1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372 2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html 3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html GMAT online Tutor Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 6390 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: If 0.010<x-√5<0.011, approximation of 1/√5-1/x is which of the followi [#permalink] Show Tags 19 Oct 2017, 00:03 => 1/√5-1/x = x-√5/x√5 From 0.010<x-√5<0.011, we have 0.010 + √5<x <0.011 + √5. We have 1/0.010+ √5 < 1/x < 1/0.011+ √5 or 1/0.010√5+5 < 1/x√5 < 1/0.011√5+5. 0.010/0.010√5+5 < x-√5/x√5 < 0.011/0.011√5+5. The approximation of x-√5/x√5 is 0.01/5=0.002 Thus, the answer is B. Answer: B _________________ MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only$99 for 3 month Online Course"
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Re: If 0.010<x-√5<0.011, approximation of 1/√5-1/x is which of the followi  [#permalink]

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14 Nov 2017, 06:35
1
chetan2u wrote:
MathRevolution wrote:
[GMAT math practice question]

If 0.010<x-√5<0.011, approximation of 1/√5-1/x is which of the following options?

A. 0.01
B. 0.002
C. 0.02
D. 0.003
E. 0.03

0.010<x-√5<0.011........ basically means x-√5~0....x~√5...

Let's see the equation now..
$$\frac{1}{√5}-\frac{1}{x}=\frac{x-√5}{x√5}=\frac{0.010}{√5*√5}=0.002$$

B

Hi Chetan if x is approx √5 then how did we get .010 in the numerator.
Re: If 0.010<x-√5<0.011, approximation of 1/√5-1/x is which of the followi &nbs [#permalink] 14 Nov 2017, 06:35
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