It is currently 19 Nov 2017, 07:27

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Confirm Cancel

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

If K = (1/(3a) + 1/b)/(5/(ab)) and ab ≠ 0, what is the value of K ?

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Expert Post
1 KUDOS received
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 42247

Kudos [?]: 132677 [1], given: 12331

If K = (1/(3a) + 1/b)/(5/(ab)) and ab ≠ 0, what is the value of K ? [#permalink]

Show Tags

New post 18 Jun 2015, 02:53
1
This post received
KUDOS
Expert's post
1
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

69% (00:56) correct 31% (01:13) wrong based on 93 sessions

HideShow timer Statistics

If \(K = \frac{\frac{1}{3a} + \frac{1}{b}}{\frac{5}{ab}}\) and ab ≠ 0, what is the value of K ?

(1) a = 3
(2) b – 3(5 – a ) = 0

Kudos for a correct solution.
[Reveal] Spoiler: OA

_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Kudos [?]: 132677 [1], given: 12331

1 KUDOS received
Board of Directors
User avatar
G
Joined: 01 Sep 2010
Posts: 3372

Kudos [?]: 9283 [1], given: 1168

Re: If K = (1/(3a) + 1/b)/(5/(ab)) and ab ≠ 0, what is the value of K ? [#permalink]

Show Tags

New post 18 Jun 2015, 03:08
1
This post received
KUDOS

Kudos [?]: 9283 [1], given: 1168

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 42247

Kudos [?]: 132677 [0], given: 12331

Re: If K = (1/(3a) + 1/b)/(5/(ab)) and ab ≠ 0, what is the value of K ? [#permalink]

Show Tags

New post 22 Jun 2015, 05:18
Bunuel wrote:
If \(K = \frac{\frac{1}{3a} + \frac{1}{b}}{\frac{5}{ab}}\) and ab ≠ 0, what is the value of K ?

(1) a = 3
(2) b – 3(5 – a ) = 0

Kudos for a correct solution.


MANHATTAN GMAT OFFICIAL SOLUTION:

It should be evident that the two statements combined are sufficient to answer the question—you can plug the value of a from Statement (1) into Statement (2) to solve for the value of b, then you can plug those values into the question to solve for K.

Immediately be skeptical. C should seem too easy. After all, you didn't do anything to the question stem. So you should do some work to determine whether one of the two statements alone (or, in some cases, each statement alone) is sufficient to answer the question.

Let's start by rephrasing the question:

\(K = \frac{\frac{1}{3a} + \frac{1}{b}}{\frac{5}{ab}}=\frac{\frac{b}{3ab} + \frac{3a}{3ab}}{\frac{5}{ab}}=\frac{b+3a}{3ab}*\frac{ab}{5}=\frac{b+3a}{15}\)

“What is the value of K?” rephrases to “What is the value of b + 3a?” Statement (2) rephrases and gives us the answer:
b – 3(5 – a) =
b – 15 + 3a = 0
b + 3a = 15

The correct answer is B.

This is not a tactic to use at lower levels of the test. On 500-600 level problems, the two statements may work together in straightforward ways to produce sufficiency. The C trap may be the C answer!
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Kudos [?]: 132677 [0], given: 12331

Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 15690

Kudos [?]: 282 [0], given: 0

Premium Member
Re: If K = (1/(3a) + 1/b)/(5/(ab)) and ab ≠ 0, what is the value of K ? [#permalink]

Show Tags

New post 22 Jun 2017, 04:17
1
This post was
BOOKMARKED
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________

GMAT Books | GMAT Club Tests | Best Prices on GMAT Courses | GMAT Mobile App | Math Resources | Verbal Resources

Kudos [?]: 282 [0], given: 0

Director
Director
avatar
S
Joined: 12 Nov 2016
Posts: 794

Kudos [?]: 36 [0], given: 165

Re: If K = (1/(3a) + 1/b)/(5/(ab)) and ab ≠ 0, what is the value of K ? [#permalink]

Show Tags

New post 10 Sep 2017, 13:31
Bunuel wrote:
If \(K = \frac{\frac{1}{3a} + \frac{1}{b}}{\frac{5}{ab}}\) and ab ≠ 0, what is the value of K ?

(1) a = 3
(2) b – 3(5 – a ) = 0

Kudos for a correct solution.


Always try to rewrite the original equation in ds suff to find the true question

St 1

Still cannot solve for b +3a

St 2

Distribute (though this was a foiling question at first).

b- 15+3a= -
b+3a= 15

suff

B
Attachments

image1.JPG
image1.JPG [ 662.54 KiB | Viewed 143 times ]

Kudos [?]: 36 [0], given: 165

Re: If K = (1/(3a) + 1/b)/(5/(ab)) and ab ≠ 0, what is the value of K ?   [#permalink] 10 Sep 2017, 13:31
Display posts from previous: Sort by

If K = (1/(3a) + 1/b)/(5/(ab)) and ab ≠ 0, what is the value of K ?

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.