negative fractional exponents

Expert replies

Previous Topic Next Topic

fastordie: Newbie | Next Rank: 10 Posts; Posts: 1; Joined: Thu Feb 19, 2009 4:48 pm

by fastordie » Fri Feb 20, 2009 8:46 am

I'm having the worst time coming up with the answer. Please help.

(sqrt (6.4 * 10^-n)^(-1/3)) = 5 When n=?

Thanks

Like this post

Source: Beat The GMAT — Problem Solving | Fri Feb 20, 2009 8:46 am

stubbornp: Master | Next Rank: 500 Posts; Posts: 496; Joined: Sun May 04, 2008 11:01 pm; Location: mumbai; Thanked: 7 times; GMAT Score:640

Re: negative fractional exponents

by stubbornp » Fri Feb 20, 2009 9:20 am

fastordie wrote:I'm having the worst time coming up with the answer. Please help.

(sqrt (6.4 * 10^-n)^(-1/3)) = 5 When n=?

Thanks

First take the left part

(sqrt (6.4 * 10^-n)^(-1/3))

(6.4 / 10^n)^ 1/2*-1/3=> (6.4 /10^n)^-1/6

=>64/(10^n+1))^-1/6 =>( (10^n+1) * 64)^1/6

=> ( (10^n+1) / 64)^1/6 =>( (10^n+1) ^1/6 ) / 64^1/6
=>( (10^n+1) ^1/6 ) /2 = 5 (As per the given)

(10^n+1) ^1/6 =10

(10^n+1 ) =10^6

=> n+1=6 => n=5

Hope it helps

Like this post

marcusking: Master | Next Rank: 500 Posts; Posts: 106; Joined: Wed Feb 04, 2009 6:09 am; Location: Louisville, KY; Thanked: 8 times

Re: negative fractional exponents

by marcusking » Fri Feb 20, 2009 10:03 am

stubbornp wrote: First take the left part

(sqrt (6.4 * 10^-n)^(-1/3))

(6.4 / 10^n)^ 1/2*-1/3=> (6.4 /10^n)^-1/6

=>64/(10^n+1))^-1/6 =>( (10^n+1) * 64)^1/6

=> ( (10^n+1) / 64)^1/6 =>( (10^n+1) ^1/6 ) / 64^1/6
=>( (10^n+1) ^1/6 ) /2 = 5 (As per the given)

(10^n+1) ^1/6 =10

(10^n+1 ) =10^6

=> n+1=6 => n=5

Hope it helps

how did you go from ( (10^n+1) * 64)^1/6 to ( (10^n+1) / 64)^1/6 ???
I think you may have left off a sign or something.

Like this post

awesomeusername: Master | Next Rank: 500 Posts; Posts: 226; Joined: Tue Jan 13, 2009 1:27 pmFollowed by: 1 member; Thanked: 23 times

by awesomeusername » Fri Feb 20, 2009 4:46 pm

What I did.

Attachments

Constant dripping hollows out a stone.
-Lucretius

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

560 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review