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Founder  Joined: 18 Apr 2015
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7x^2=21 [#permalink]
Expert's post 00:00

Question Stats: 100% (00:26) correct 0% (00:00) wrong based on 6 sessions
$$7x^2=21$$

 Quantity A Quantity B x 2

A)The quantity in Column A is greater.
B)The quantity in Column B is greater.
C)The two quantities are equal.
D)The relationship cannot be determined from the information given.

Kudos for the right answer and explanation
[Reveal] Spoiler: OA

_________________ GRE Instructor Joined: 10 Apr 2015
Posts: 2311
Followers: 73

Kudos [?]: 2208  , given: 27

Re: 7x^2=21 [#permalink]
1
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Expert's post
Carcass wrote:
$$7x^2=21$$

 Quantity A Quantity B x 2

A)The quantity in Column A is greater.
B)The quantity in Column B is greater.
C)The two quantities are equal.
D)The relationship cannot be determined from the information given.

Kudos for the right answer and explanation

GIVEN: $$7x^2=21$$

Divide both sides by 7 to get: $$x^2=3$$

So, EITHER $$x=\sqrt{3}$$ or $$x=-\sqrt{3}$$

ASIDE: By test day, it's useful to have the following approximations memorized:
√2 ≈ 1.4
√3 ≈ 1.7
√5 ≈ 2.2

So, we know that EITHER $$x≈1.7$$ or $$x≈-1.7$$
Since $$1.7<2$$ and $$-1.7<2$$, we can see that Quantity B is greater than Quantity A

Answer: B

Cheers,
Brent
_________________

Brent Hanneson – Creator of greenlighttestprep.com Sign up for my free GRE Question of the Day emails

Intern Joined: 15 Aug 2019
Posts: 31
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Kudos [?]: 20 , given: 3

Re: 7x^2=21 [#permalink]
7x^2 = 21
=> x^2 = 3
=> x = +3^(1/2) or -3^(1/2)

It is clear that -3^(1/2) < 2;
In case of +3^(1/2): 3^(1/2) < 4^(1/2) => 3^(1/2) < 2
So ans is B. Re: 7x^2=21   [#permalink] 16 Aug 2019, 08:43
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