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• ### $450 Tuition Credit & Official CAT Packs FREE December 15, 2018 December 15, 2018 10:00 PM PST 11:00 PM PST Get the complete Official GMAT Exam Pack collection worth$100 with the 3 Month Pack ($299) # Which of the following is the closest value of x such that  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics Author Message TAGS: ### Hide Tags Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 6639 GMAT 1: 760 Q51 V42 GPA: 3.82 Which of the following is the closest value of x such that [#permalink] ### Show Tags 07 Jun 2017, 00:23 1 10 00:00 Difficulty: 65% (hard) Question Stats: 56% (02:13) correct 44% (02:25) wrong based on 137 sessions ### HideShow timer Statistics Which of the following is the closest value of x such that $$x^{20}+x^2+0.0000019=0.09$$? A. 0.1 B. 0.01 C. 0.3 D. 0.03 E. 0.003 _________________ 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: Which of the following is the closest value of x such that  [#permalink]

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07 Jun 2017, 00:36
2
2
MathRevolution wrote:
Which of the following is the closest value of x such that $$x^{20}+x^2+0.0000019=0.09$$?
A. 0.1
B. 0.01
C. 0.3
D. 0.03
E. 0.003

$$x^{20}+x^2+0.0000019=0.09$$

Nice Question
Rather than testing options, one of the best way to solve the solve is to reduce the variables
$$x^{20}+x^2+0.0000019=0.09$$
Reduced to
$$x^2+0.0000019=0.09$$
Reduced to
$$x^2=0.09$$

Voila, x = 0.3

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Which of the following is the closest value of x such that  [#permalink]

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07 Jun 2017, 07:12
1
Top Contributor
3
MathRevolution wrote:
Which of the following is the closest value of x such that $$x^{20}+x^2+0.0000019=0.09$$?

A. 0.1
B. 0.01
C. 0.3
D. 0.03
E. 0.003

When a GMAT question tells us to find the "closest value" or the "approximate value," this usually gives us the go ahead to estimate.

First recognize that, for all 5 answer choices, the value of x^20 becomes inconsequential
For example, if x = 0.1, then x^20 = (0.1)^20 = (1/10)^20 = 1/100000000000000000000
The same applies to all 5 answer choices.

Since the value of x^20 has almost no effect on the equation, we can safely ignore it.

Likewise, the value 0.0000019 is very very very small in relation to 0.09
So, we can safely ignore it.

So, our equation becomes x² ≈ 0.09
Solve to get: x ≈ 0.3

Cheers,
Brent
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Re: Which of the following is the closest value of x such that  [#permalink]

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09 Jun 2017, 01:35
==> From $$x^{20}+x^2+0.0000019=0.09, x^{20}$$ and 0.0000019 are very close to 0, so you can ignore them, and the equation becomes $$x^2=0.09=0.3^2$$. Thus, you get x=0.3.

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Re: Which of the following is the closest value of x such that  [#permalink]

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09 Jun 2017, 07:41
Imo C we can do this question by approximations
Ignore x^20 and 0.0000019
Thus we have
X^2 =0.09

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Re: Which of the following is the closest value of x such that  [#permalink]

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