Live GMAT classes with Target Test Prep start Nov 21 and Nov 22. First class free.

See classes
Target Test Prep · GMAT

Choose how you want to prepare

Learn live with an expert or move at your own pace. Every option includes the complete TTP study system.

Newsweek Readers’ Choice Awards 2026 winner: Target Test Prep, #1 Test Prep

Target Test Prep was voted #1 Best Test Prep in the 2026 Newsweek Readers’ Choice™ Awards.

★★★★★5.0563 reviews
GMATLiveTeachStarts Nov 22
Josh Braslow, Target Test Prep GMAT expert
LIVE ONLINE CLASSES

Get Ready for GMAT Test Day Faster with Live Online Classes

with Josh Braslow, 20+ years in test prep

Nov 22 · Josh Braslow
Sun · 9:30 AM to 12:30 PM ET
Included
40 hours of live online classes + 6 months of TTP OnDemand
  • Attend the first class for free
  • Every class is recorded, so you never fall behind
View classes & enroll
Limited seats availableTarget Test Prep
EALiveTeachOnDemandStart anytime
EXECUTIVE ASSESSMENT

Target Test Prep EA OnDemand

Self-paced EA prep. Study on your schedule.

EXECUTIVE ASSESSMENT

with

165+ EA score guarantee
$05-day trial no automatic billing
Schedule
Included
40 hours of live online classes plus six months of access to the complete TTP EA OnDemand course.
  • 165+ EA Score Guarantee
  • 4,100+ Quant, Verbal, and Integrated Reasoning practice questions
  • 400+ hours of in-depth video lessons
  • 3,000+ step-by-step video solutions
View EA class & enroll Start free 5-day trial
Limited cohort · enrollment openTrial includes full course accessTarget Test Prep
GMATOnDemandStart anytime
SELF-PACED MASTERCLASS

Target Test Prep GMAT OnDemand

Complete access from day one. Study on your schedule.

715+ score guarantee
$0to start then $127/mo
  • Personalized study plan and analytics
  • Thousands of lessons and practice questions
Start free 5-day trial
Read 563 reviewsTarget Test Prep

Rato question

Expert replies
Post new topic Post Reply
Subscribe topic
Previous Topic Next Topic

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16206
Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members
Location: Vancouver, BC
Thanked: 5254 times
GMAT Score:770
by Brent@GMATPrepNow » Sat Dec 13, 2008 11:07 am
Here's one for you:

The current ratio of boys to girls at a certain school is 2 to 5. If 12 additional boys were added to the school, the new ratio of boys to girls would be 4 to 9. How many boys currently attend the school?

(A) 27
(B) 48
(C) 54
(D) 72
(E) 108
Top
Join the discussion
Source: — Problem Solving |
User avatar
Community Manager
Posts: 1049
Joined: Sun Apr 06, 2008 5:15 pmFollowed by: 27 members
Location: Pittsburgh, PA
Thanked: 113 times
GMAT Score:710

by dmateer25 » Sat Dec 13, 2008 11:52 am
Let x = Total students
Let y = current boys

2x/7 = y
x = 7y/2..............(1)

(4x + 48)/13 = y + 12
4x + 48 = 13y + 156.......................(2)


4(7y/2) + 48 = 13y + 156
28y/2 + 48 = 13 y + 156
14y = 13y + 108
y = 108

E
Top
Join the discussion

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16206
Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members
Location: Vancouver, BC
Thanked: 5254 times
GMAT Score:770

by Brent@GMATPrepNow » Sat Dec 13, 2008 11:55 am
That's pretty good, but the answer can be found faster by using just one variable.
Anyone?
Top
Join the discussion
User avatar
Community Manager
Posts: 1049
Joined: Sun Apr 06, 2008 5:15 pmFollowed by: 27 members
Location: Pittsburgh, PA
Thanked: 113 times
GMAT Score:710

by dmateer25 » Sat Dec 13, 2008 12:50 pm
With 1 variable:

Let x= # of original boys

(x/1) / (2/7) + 12 = ((x+12)/1) / (4/13)

7x/2 + 12 = (13x+156)/4

(7x + 24)/2 = (13x+156)/4

(14x + 48)/4 - (13x + 156)/4

x - 108 = 0

x = 108
Top
Join the discussion

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16206
Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members
Location: Vancouver, BC
Thanked: 5254 times
GMAT Score:770

by Brent@GMATPrepNow » Sat Dec 13, 2008 5:27 pm
The OA is E.

Here's my method:
Let 2x be the number of boys currently attending the school.
This means that the number of girls is 5x

If we add 12 boys (to the existing 2x boys), the new ratio becomes 4/9.
This gives us the equation (2x+12)/5x = 4/9

Solve for 2x (since there are currently 2x boys) and you get 2x=108


Another method (if you're stuck) is to start plugging in answer choices.
Top
Join the discussion
User avatar
Legendary Member
Posts: 2134
Joined: Mon Oct 20, 2008 11:26 pmFollowed by: 25 members
Thanked: 237 times
GMAT Score:730

Re: Rato question

by logitech » Sat Dec 13, 2008 6:17 pm
Okay, the girls numbers dont change so only the TOP part of the B/G fraction changes

LCM(5:9)=45 so simply multiply the first boys with 9 and second boys with 5

18B+12=20B , so B is 6 and 18B is 108
LGTCH
---------------------
"DON'T LET ANYONE STEAL YOUR DREAM!"
Top
Join the discussion