It is currently Mon Sep 16, 2019 11:14 pm

 All times are UTC - 5 hours [ DST ]

 Page 1 of 1 [ 2 posts ]
 Print view Previous topic | Next topic
Author Message
 Post subject: GMAT AlgebraPosted: Mon Apr 29, 2013 11:34 am

Joined: Sun May 30, 2010 3:15 am
Posts: 424
If 1/3 + 1/2 + 1/x = 4, then x =
A. 5/18
B. 6/19
C. 24/11
D. 19/6
E. 18/5

(B) To solve this equation, we first need to find a common denominator to simplify the equation. The lowest common denominator is 3 × 2 × x = 6x. If we multiply the both sides of the equation by 6x, we can get rid of all of the fractions.

Multiplying 1/3 + 1/2 + 1/x = 4 by 6x, we get:
6x/3 + 6x/2 + 6x/x = 4(6x).

Reducing this, we get:
2x + 3x + 6 = 24x
5x + 6 = 24x
6 = 19x, or x = 6/19.

Now you might be tempted to stop there, but if you have extra time you can double check by backsolving in for x. You can plug in 6/19 for x. 1/(6/19) is the same as 19/6.
1/2 = 3/6 and 1/3 = 2/6 so you can put everything in terms of 6ths and get:
2/6 + 3/6 + 19/6 = 24/6 = 4.

So, you can see with 100% certainty that the answer of 6/19 is correct.

The correct answer is choice (B).
----------
Hi.
I didn't understand why we have to multiply both sides of the equation.
What I did is finding LCD that is 6, and I did not multiply 4 by 6...

Also, I didn't understand what is 19/6 ?

Thanks!

Top

 Post subject: Re: GMAT AlgebraPosted: Mon Apr 29, 2013 11:35 am

Joined: Sun May 30, 2010 2:23 am
Posts: 498

Top

 Display posts from previous: All posts1 day7 days2 weeks1 month3 months6 months1 year Sort by AuthorPost timeSubject AscendingDescending
 Page 1 of 1 [ 2 posts ]

 All times are UTC - 5 hours [ DST ]

#### Who is online

Users browsing this forum: Google [Bot] and 2 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