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# √m4=64 and m>0, what is the value of cubic root of m?

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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
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√m4=64 and m>0, what is the value of cubic root of m?  [#permalink]

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06 Jul 2017, 01:27
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Question Stats:

85% (00:46) correct 15% (01:01) wrong based on 67 sessions

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$$√m^4=64$$ and m>0, what is the value of cubic root of m?

A. 1
B. 2
C. 4
D. 8
E. 16

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"Only $149 for 3 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself" Senior PS Moderator Joined: 26 Feb 2016 Posts: 3386 Location: India GPA: 3.12 √m4=64 and m>0, what is the value of cubic root of m? [#permalink] ### Show Tags 06 Jul 2017, 02:34 Since $$√m^4=64$$, $$m^2$$ will be equal to 64. m can take value 8 or -8(which is eliminated as m>0) Therefore, m=8 The cube root of m is 2(Option B) _________________ You've got what it takes, but it will take everything you've got Manager Joined: 14 Apr 2017 Posts: 248 Location: India sandeep : sharma Concentration: International Business, Entrepreneurship GPA: 3.9 Re: √m4=64 and m>0, what is the value of cubic root of m? [#permalink] ### Show Tags 06 Jul 2017, 03:08 √m4 = m2 = 64 that means m=8=2*2*2 so cube root of m = 2 hence b _________________ Senior Manager Joined: 28 Jun 2015 Posts: 290 Concentration: Finance GPA: 3.5 Re: √m4=64 and m>0, what is the value of cubic root of m? [#permalink] ### Show Tags 06 Jul 2017, 03:36 MathRevolution wrote: $$√m^4=64$$ and m>0, what is the value of cubic root of m? A. 1 B. 2 C. 4 D. 8 E. 16 $$\sqrt{m^{4}} = 64.$$ Squaring on both sides, we get $$m^{4} = 64^{2}$$ So, $$m^{2} = 64$$, hence, $$m = 8$$ (given: $$m > 0$$) Cube root of 8 = 2. Ans - B. _________________ I used to think the brain was the most important organ. Then I thought, look what’s telling me that. Director Joined: 04 Dec 2015 Posts: 750 Location: India Concentration: Technology, Strategy WE: Information Technology (Consulting) Re: √m4=64 and m>0, what is the value of cubic root of m? [#permalink] ### Show Tags 06 Jul 2017, 04:46 1 MathRevolution wrote: $$√m^4=64$$ and m>0, what is the value of cubic root of m? A. 1 B. 2 C. 4 D. 8 E. 16 $$\sqrt{m^4}=64$$ $$m^{\frac{4}{2}}$$ $$= 64$$ $$m^2 = 64$$ $$m = +8$$ or $$-8$$ Given $$m>0$$. Therefore; $$m = 8$$ We need to find the value of Cubic root of $$m$$ $$\sqrt[3]{m} = \sqrt[3]{8} = 2$$ Answer (B)... _________________ Please Press "+1 Kudos" to appreciate. Board of Directors Status: QA & VA Forum Moderator Joined: 11 Jun 2011 Posts: 4423 Location: India GPA: 3.5 WE: Business Development (Commercial Banking) Re: √m4=64 and m>0, what is the value of cubic root of m? [#permalink] ### Show Tags 06 Jul 2017, 08:07 MathRevolution wrote: $$√m^4=64$$ and m>0, what is the value of cubic root of m? A. 1 B. 2 C. 4 D. 8 E. 16 $$√m^4=64$$ So, $$√m^2=8^2$$ Or, $$m = 8$$ Hence, $$^3√m=2$$ Thus, answer will be (B) 2 _________________ Thanks and Regards Abhishek.... PLEASE FOLLOW THE RULES FOR POSTING IN QA AND VA FORUM AND USE SEARCH FUNCTION BEFORE POSTING NEW QUESTIONS How to use Search Function in GMAT Club | Rules for Posting in QA forum | Writing Mathematical Formulas |Rules for Posting in VA forum | Request Expert's Reply ( VA Forum Only ) Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 7236 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: √m4=64 and m>0, what is the value of cubic root of m? [#permalink] ### Show Tags 09 Jul 2017, 18:26 ==> You get $$√m^4=64=2^6, m^4=(2^6)^2=2^{12}.$$ Then, you get $$m=(2^{12})^{\frac{1}{4}}=2^3$$, and from 3√m=3$$\sqrt{2^3}$$=2, the answer is B. Answer: B _________________ 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$149 for 3 month Online Course"
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Re: √m4=64 and m>0, what is the value of cubic root of m?  [#permalink]

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14 Jul 2017, 10:36
MathRevolution wrote:
$$√m^4=64$$ and m>0, what is the value of cubic root of m?

A. 1
B. 2
C. 4
D. 8
E. 16

Let’s solve for m:

√(m^4) = 64

(m^4)^(½) = 64

m^2 = 64

|m| = √64

|m| = 8

m = 8 or m = -8

Since m > 0, m = 8.

Thus, the cube root of m is 2.

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Re: √m4=64 and m>0, what is the value of cubic root of m?   [#permalink] 14 Jul 2017, 10:36
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