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# given 8z^4 = 96

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Joined: 07 Jun 2014
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given 8z^4 = 96 [#permalink]  02 Jul 2017, 15:31
Expert's post
00:00

Question Stats:

76% (00:48) correct 23% (00:43) wrong based on 26 sessions
$$8z^4 = 96$$

 Quantity A Quantity B 2 z

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

Drill 1
Question: 2
Page: 352
[Reveal] Spoiler: OA

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Sandy
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Kudos [?]: 1337 [0], given: 8

Re: given 8z^4 = 96 [#permalink]  06 Jul 2017, 05:50
Expert's post
sandy wrote:
$$8z^4 = 96$$

 Quantity A Quantity B 2 z

Given: $$8z^4 = 96$$

Divide both sides by 8 to get: $$z^4 = 12$$

So, EITHER z = ∜12 OR z = -∜12

Notice that ∜1 = 1 and ∜16 = 2. So ∜12 must be BETWEEN 1 and 2.

We can say ∜12 = 1.something and -∜12 = -1.something

Since 1.something and -1.something are both smaller than 2, we can conclude that Quantity A is greater.

[Reveal] Spoiler:
A

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GRE Prep Club Legend
Joined: 07 Jun 2014
Posts: 4856
GRE 1: Q167 V156
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Kudos [?]: 1731 [1] , given: 397

Re: given 8z^4 = 96 [#permalink]  22 Apr 2018, 14:05
1
KUDOS
Expert's post
Explanation

Divide both sides by 8 to get $$z^4 = 12$$. Rather than finding the fourth root of 12, try plugging in 2 for z: $$2^4 = 16$$, so z must be less than 2. Of course, z may be negative, but any negative number is also less than 2.

Hence option A is correct!
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Re: given 8z^4 = 96   [#permalink] 22 Apr 2018, 14:05
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