It is currently 25 Feb 2018, 05:53

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

In a certain calculus class, the ratio of the number of math majors to

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

Hide Tags

Senior Manager
Senior Manager
avatar
Joined: 30 Aug 2003
Posts: 317
Location: dallas , tx
In a certain calculus class, the ratio of the number of math majors to [#permalink]

Show Tags

New post 21 Nov 2003, 13:10
4
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

81% (01:24) correct 19% (01:46) wrong based on 188 sessions

HideShow timer Statistics

In a certain calculus class, the ratio of the number of math majors to the number of students who are not math majors is 2 to 5. If 2 more math majors were to enter the class, the ratio would be 1 to 2. How many students are in the class?

A. 10
B. 12
C. 21
D. 28
E. 35
[Reveal] Spoiler: OA

_________________

shubhangi


Last edited by Bunuel on 03 Apr 2015, 03:21, edited 1 time in total.
Renamed the topic, edited the question, added the OA and moved to PS forum.
1 KUDOS received
Director
Director
User avatar
Joined: 28 Oct 2003
Posts: 501
Location: 55405
Re: In a certain calculus class, the ratio of the number of math majors to [#permalink]

Show Tags

New post 21 Nov 2003, 13:41
1
This post received
KUDOS
My way of solving:

The number of students is a multiple of seven. Rule out A and B.

That leaves C, D, and E: 21,28,35, or, 6/15, 8/20, 10/25.

To get 50% (a fraction that reduces to 1/2), you must have an EVEN denominator.

D is the only possible solution.
3 KUDOS received
Senior Manager
Senior Manager
avatar
Joined: 23 Sep 2003
Posts: 292
Location: US
Re: In a certain calculus class, the ratio of the number of math majors to [#permalink]

Show Tags

New post 21 Nov 2003, 14:40
3
This post received
KUDOS
1
This post was
BOOKMARKED
Another easy way:

2x/5x is original ratio

(2x + 2)/5x = 1/2 new ratio
cross multiply
2(2x + 2) = 5x
x = 4

2(4) + 5(4) = 28.
Expert Post
EMPOWERgmat Instructor
User avatar
D
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 11074
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: 340 Q170 V170
Re: In a certain calculus class, the ratio of the number of math majors to [#permalink]

Show Tags

New post 03 Apr 2015, 10:14
Hi All,

Since the question asks for the total number of students in the class, and the answer choices are numbers, we can TEST THE ANSWERS.

From the prompt, we know that the current ratio of math-majors to non-math-majors is 2:5. This means that the number of math-majors MUST be a multiple of 2 and the number of non-math-majors MUST be an equivalent multiple of 5. By extension, the TOTAL number of students MUST be a multiple of 7. We're then told that adding 2 math majors to the class with change the ratio to 1:2

Since the total number of students MUST be a multiple of 7, we can eliminate Answers A and B.

Let's TEST Answer D.....
IF.....
There are 28 total students.....
math-majors = 8
non-math-majors = 20

Adding 2 more math-majors --> 8+2 = 10
Ratio of math-majors to non-math-majors is now 10:20, which is 1:2
This is a MATCH to what we were told, so this MUST be the answer.

Final Answer:
[Reveal] Spoiler:
D


GMAT assassins aren't born, they're made,
Rich
_________________

760+: Learn What GMAT Assassins Do to Score at the Highest Levels
Contact Rich at: Rich.C@empowergmat.com

Rich Cohen

Co-Founder & GMAT Assassin

Special Offer: Save $75 + GMAT Club Tests Free
  Official GMAT Exam Packs + 70 Pt. Improvement Guarantee
www.empowergmat.com/

***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***********************

Intern
Intern
User avatar
B
Status: Aspiring GMAT Assassin
Joined: 29 Nov 2015
Posts: 10
Location: United States (CO)
GPA: 3.3
WE: Law (Military & Defense)
Re: In a certain calculus class, the ratio of the number of math majors to [#permalink]

Show Tags

New post 28 Dec 2015, 01:03
I didn't pick up on the fact that the total number of students needs to be a multiple of 7. That's why we practice!

MATH:NON-MATH=2:5
M=2/5N
2/5N+2=1/2N
2=1/2N-2/5N
2=5/10N-4/10N
2=1/10N

N=20
M=2/5*20=8

TOTAL=28
Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 13755
Premium Member
Re: In a certain calculus class, the ratio of the number of math majors to [#permalink]

Show Tags

New post 10 Feb 2018, 03:00
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

Re: In a certain calculus class, the ratio of the number of math majors to   [#permalink] 10 Feb 2018, 03:00
Display posts from previous: Sort by

In a certain calculus class, the ratio of the number of math majors to

  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®.