It is currently Tue Oct 16, 2018 8:06 pm

 All times are UTC - 5 hours [ DST ]

 Page 1 of 1 [ 4 posts ]
 Print view Previous topic | Next topic
Author Message
 Post subject: GMAT AlgebraPosted: Tue Feb 22, 2011 4:44 pm

Joined: Sun May 30, 2010 3:15 am
Posts: 424
If (1/4)ª × 2³ = (1/2)³ª then a =

A. -3
B. -2
C. 0
D. 3
E. 4

(A) (1/4)ª × 2³ = 2 to the (3 – 2a)-th power.
(1/2)³ª = 2 to the (-3a)-th power.

Equality holds if powers are equal.
3 – 2a = -3a
a = -3
The correct answer is choice (A).
-----------

I don't understand how we are able to get the powers to have like numbers below them here. I understand that if your are able to get the variables or number the same then you can just set the powers equal but don't know how to come up with ther here. Thank you.

Top

 Post subject: Re: GMAT AlgebraPosted: Tue Feb 22, 2011 5:02 pm

Joined: Sun May 30, 2010 2:23 am
Posts: 498
(1/4)ª × 2³ = (1/2)³ª

We're looking for the same base, 2.
Using properties of exponents, we can see that current bases are powers of 2:

Then we can plug in the simplified terms and use properties of exponents to arrive to the final equation form:

If these transformations are NOT clear to you, you should go over the properties of exponents:
http://www.800score.com/gmat-guide.html

Top

 Post subject: Re: GMAT AlgebraPosted: Thu Jul 07, 2011 4:49 pm

Joined: Sun May 30, 2010 3:15 am
Posts: 424
How do you get this answer?
Why does (1/4)ª × 2³ = 2 in (3 – 2a)-th power?

Top

 Post subject: Re: GMAT AlgebraPosted: Thu Jul 07, 2011 5:01 pm

Joined: Sun May 30, 2010 2:23 am
Posts: 498
Take a look at the explanation above. What we do there is we use the regular properties of exponents. Take a look of how we convert (1/4)ª into 2 in the (-2a)-th power.

If something in it is unclear to you, go over the properties of exponents and try to see which ones we apply here. If you have any questions left then, fell free to ask (specifying which exact step is unclear).

Top

 Display posts from previous: All posts1 day7 days2 weeks1 month3 months6 months1 year Sort by AuthorPost timeSubject AscendingDescending
 Page 1 of 1 [ 4 posts ]

 All times are UTC - 5 hours [ DST ]

#### Who is online

Users browsing this forum: No registered users and 4 guests

 You cannot post new topics in this forumYou cannot reply to topics in this forumYou cannot edit your posts in this forumYou cannot delete your posts in this forumYou cannot post attachments in this forum

Search for:
 Jump to:  Select a forum ------------------ GMAT    GMAT: Quantitative Section (Math)    GMAT: Verbal Section    GMAT: Integrated Reasoning    GMAT: General Questions GRE    GRE: Quantitative Reasoning (Math)    GRE: Verbal Reasoning    GRE: General Questions General questions    Other questions