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What is the value of (2x 5)^3 ?

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What is the value of (2x 5)^3 ?  [#permalink]

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New post Updated on: 17 Dec 2017, 01:22
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A
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Question Stats:

68% (01:08) correct 32% (01:03) wrong based on 251 sessions

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What is the value of \((2x – 5)^3\) ?


(1) \((2x)^3 = 216\)

(2) \((2x + 3)^2 = 81\)

Originally posted by gorden on 08 Nov 2008, 20:56.
Last edited by Bunuel on 17 Dec 2017, 01:22, edited 2 times in total.
Renamed the topic, edited the question, added the OA and moved to DS forum.
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Re: What is the value of (2x 5)^3 ?  [#permalink]

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New post 08 Nov 2008, 21:06
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(1) suff as (2x)^3 = 216 will return only 1 result of x
(2) insuff as (2x + 3)^2 = 81 will return 2 results

Ans: A
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Re: What is the value of (2x 5)^3 ?  [#permalink]

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New post 19 May 2016, 18:56
gorden wrote:
What is the value of (2x – 5)^3 ?

(1) (2x)^3 = 216
(2) (2x + 3)^2 = 81


1. sufficient. 2x = sqrt(216)
identify the prime factors of 216 = 2^3 * 3^3 -> 2x=2*3 => x=3. sufficient.

2. 2 outcomes:
2x+3=9 => 2x=6 => x=3
2x+3=-9 => 2x=-12 => x=-6

not sufficient.
answer A.
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Re: What is the value of (2x 5)^3 ?  [#permalink]

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New post 18 Sep 2016, 09:19
A is correct. Here's why:

(1) 2x^3 = 216
= x^3 = 108 (if you do a 'tree', you'll see 108 factors down to 2,2,3,3,3) --> x = 3sqrt(2)

SUFFICIENT

(2) (2x+3)^2 = 81
=2x+3 = +/- 9

NOT SUFFICIENT
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Re: What is the value of (2x 5)^3 ?  [#permalink]

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New post 16 Dec 2017, 17:14
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: What is the value of (2x 5)^3 ? &nbs [#permalink] 16 Dec 2017, 17:14
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