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# 7x^2=21

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7x^2=21 [#permalink]  16 Aug 2019, 01:19
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

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Re: 7x^2=21 [#permalink]  16 Aug 2019, 05:00
1
KUDOS
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

Cheers,
Brent
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Brent Hanneson – Creator of greenlighttestprep.com

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Re: 7x^2=21 [#permalink]  16 Aug 2019, 08:43
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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