• Economist Test Prep
    Free Trial & Practice Exam
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    Economist Test Prep
  • Veritas Prep
    Free Veritas GMAT Class
    Experience Lesson 1 Live Free

    Available with Beat the GMAT members only code

    MORE DETAILS
    Veritas Prep
  • Target Test Prep
    5-Day Free Trial
    5-day free, full-access trial TTP Quant

    Available with Beat the GMAT members only code

    MORE DETAILS
    Target Test Prep
  • PrepScholar GMAT
    5 Day FREE Trial
    Study Smarter, Not Harder

    Available with Beat the GMAT members only code

    MORE DETAILS
    PrepScholar GMAT
  • Magoosh
    Magoosh
    Study with Magoosh GMAT prep

    Available with Beat the GMAT members only code

    MORE DETAILS
    Magoosh
  • EMPOWERgmat Slider
    1 Hour Free
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    EMPOWERgmat Slider
  • Kaplan Test Prep
    Free Practice Test & Review
    How would you score if you took the GMAT

    Available with Beat the GMAT members only code

    MORE DETAILS
    Kaplan Test Prep
  • The Princeton Review
    FREE GMAT Exam
    Know how you'd score today for $0

    Available with Beat the GMAT members only code

    MORE DETAILS
    The Princeton Review
  • Varsity Tutors
    Award-winning private GMAT tutoring
    Register now and save up to $200

    Available with Beat the GMAT members only code

    MORE DETAILS
    Varsity Tutors
  • e-gmat Exclusive Offer
    Get 300+ Practice Questions
    25 Video lessons and 6 Webinars for FREE

    Available with Beat the GMAT members only code

    MORE DETAILS
    e-gmat Exclusive Offer

Nice fast way??

This topic has 4 expert replies and 0 member replies
boomgoesthegmat Senior | Next Rank: 100 Posts Default Avatar
Joined
25 Apr 2016
Posted:
93 messages
Upvotes:
1

Nice fast way??

Post Mon Apr 25, 2016 2:37 pm
Which of the following is the value of squareroot[cuberoot(0.000064)]?

A) 0.004
B) 0.008
C) 0.02
D) 0.04
E) 0.2

Answer: E

  • +1 Upvote Post
  • Quote
  • Flag

GMAT/MBA Expert

Post Mon Apr 25, 2016 2:58 pm
boomgoesthegmat wrote:
Which of the following is the value of squareroot[cuberoot(0.000064)]?

A) 0.004
B) 0.008
C) 0.02
D) 0.04
E) 0.2
[ (0.000064)^(1/3) ]^1/2

= (64 * 10¯⁶)^(1/6)

= (64)^(1/6) * (10¯⁶)^(1/6)

= 2 * 10¯¹

= 0.2

The correct answer is E.

_________________
Mitch Hunt
GMAT Private Tutor
GMATGuruNY@gmail.com
If you find one of my posts helpful, please take a moment to click on the "UPVOTE" icon.
Available for tutoring in NYC and long-distance.
For more information, please email me at GMATGuruNY@gmail.com.

  • +1 Upvote Post
  • Quote
  • Flag
Free GMAT Practice Test How can you improve your test score if you don't know your baseline score? Take a free online practice exam. Get started on achieving your dream score today! Sign up now.

GMAT/MBA Expert

Post Mon Apr 25, 2016 3:36 pm
boomgoesthegmat wrote:
Which of the following is the value of squareroot[cuberoot(0.000064)]?

A) 0.004
B) 0.008
C) 0.02
D) 0.04
E) 0.2
Another approach:

√[∛(0.000064)] = √[∛(64/1,000,000)]
= √[(4/100)]
= 2/10
= 0.2
= C

Here are some related resources that cover the concepts needed to solve this question:
- Conversions with fractions and decimals: https://www.gmatprepnow.com/module/gmat-arithmetic/video/1066
- Introduction to square roots: https://www.gmatprepnow.com/module/gmat-powers-and-roots/video/1033
- Other roots: https://www.gmatprepnow.com/module/gmat-powers-and-roots/video/1035

Cheers,
Brent

_________________
Brent Hanneson – Founder of GMATPrepNow.com
Use our video course along with Beat The GMAT's free 60-Day Study Guide

Check out the online reviews of our course
Come see all of our free resources

  • +1 Upvote Post
  • Quote
  • Flag
GMAT Prep Now's comprehensive video course can be used in conjunction with Beat The GMAT’s FREE 60-Day Study Guide and reach your target score in 2 months!

GMAT/MBA Expert

Matt@VeritasPrep GMAT Instructor
Joined
12 Sep 2012
Posted:
2637 messages
Followed by:
114 members
Upvotes:
625
Target GMAT Score:
V51
GMAT Score:
780
Post Wed Apr 27, 2016 2:12 pm
I'd think of it as

.000064^(1/2 * 1/3) =>

.000064^(1/6)

Since 2⁶ = 64, this suggests that the answer is .02 or .2. Then we might notice that .000064 has SIX decimal places. .2⁶ will also have six decimal places, so that MUST be our answer!

  • +1 Upvote Post
  • Quote
  • Flag
Enroll in a Veritas Prep GMAT class completely for FREE. Wondering if a GMAT course is right for you? Attend the first class session of an actual GMAT course, either in-person or live online, and see for yourself why so many students choose to work with Veritas Prep. Find a class now!
Post Thu Mar 15, 2018 9:26 am
boomgoesthegmat wrote:
Which of the following is the value of squareroot[cuberoot(0.000064)]?

A) 0.004
B) 0.008
C) 0.02
D) 0.04
E) 0.2
To solve this question, we can refer to two rules:

1) If a decimal with a finite number of decimal places is a perfect cube, its cube root will have exactly one-third of the number of decimal places. Thus, a perfect cube decimal must have a number of decimal places that is a multiple of 3.

2) If a decimal with a finite number of decimal places is a perfect square, its square root will have exactly half of the number of decimal places. Thus, a perfect square decimal must have an even number of decimal places.

Let's look first at cuberoot(0.000064). By rule number 1, the cube root of 0.000064 = 0.04. We were able obtain this value because 0.000064 has 6 DECIMAL PLACES, and because the cube root of 64 is 4.

The problem now looks like this: squareroot(0.04). By rule number 2, the square root of 0.04 = 0.2. We were able to obtain this value because 0.04 has 2 DECIMAL PLACES, and the square root of 4 is 2.

Alternate Solution:

First, we note that taking the cube root of the square root of a number is equivalent to taking the sixth root of the number.

Next, let’s write 0.000064 = 64/1000000 = 2^6/10^6. Taking sixth root, we obtain 2/10 = 0.2.

Answer: E

_________________
Scott Woodbury-Stewart Founder and CEO

  • +1 Upvote Post
  • Quote
  • Flag

Top First Responders*

1 GMATGuruNY 72 first replies
2 Rich.C@EMPOWERgma... 45 first replies
3 Brent@GMATPrepNow 43 first replies
4 Jay@ManhattanReview 27 first replies
5 ErikaPrepScholar 9 first replies
* Only counts replies to topics started in last 30 days
See More Top Beat The GMAT Members

Most Active Experts

1 image description GMATGuruNY

The Princeton Review Teacher

133 posts
2 image description Rich.C@EMPOWERgma...

EMPOWERgmat

118 posts
3 image description Jeff@TargetTestPrep

Target Test Prep

105 posts
4 image description Max@Math Revolution

Math Revolution

93 posts
5 image description Scott@TargetTestPrep

Target Test Prep

92 posts
See More Top Beat The GMAT Experts