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

probability

Expert replies
Post new topic Post Reply
Subscribe topic
Previous Topic Next Topic
Legendary Member
Posts: 876
Joined: Thu Apr 10, 2008 8:14 am
Thanked: 13 times
by ketkoag » Wed Jun 10, 2009 9:27 am
What is the total number of some green balls and yellow balls?
1) The probability that a ball randomly selected is green is 1/10
2) One green ball picked out at fist, the probability that another ball randomly selected is green is 3/8.

[spoiler]please confirm the answer, IMO : E[/spoiler]
Top
Join the discussion
Source: — Data Sufficiency |
Senior | Next Rank: 100 Posts
Posts: 93
Joined: Thu Apr 10, 2008 1:42 pm
Location: Chicago
Thanked: 20 times

by Musiq » Wed Jun 10, 2009 9:32 am
Ketkoag,

May I ask where you got this question from....it's not very GMAT-like.

The answer is E, because there could be other colors of balls present...no where are we told that the only two kinds of balls are Green and Yellow.
For love, not money.
Top
Join the discussion
Master | Next Rank: 500 Posts
Posts: 159
Joined: Sun Jul 27, 2008 8:41 pm
Thanked: 3 times

by ankit1383 » Mon Aug 10, 2009 6:06 am
IMO...C
can someone confirm....(If we assume there are only two types of ball)
Top
Join the discussion
Junior | Next Rank: 30 Posts
Posts: 15
Joined: Sun Nov 11, 2007 9:58 pm
Thanked: 1 times

by aspiregmat » Mon Aug 10, 2009 6:39 am
If no other information given about other color balls its definately E.

Lets assume that there are only green and yellow balls:

1) Probability of picking a green ball = 1/10 so only thing we know is green:yellow = 1:9

2) Probability of picking a green ball in second try = 3/8 and 1 green is already out so green:yellow = 4:5 or 7:9 and so on...

combining both == again only ratios which are also not matching...

So IMO E even if we assume only green and yellow balls.
Top
Join the discussion
Master | Next Rank: 500 Posts
Posts: 159
Joined: Sun Jul 27, 2008 8:41 pm
Thanked: 3 times

by ankit1383 » Mon Aug 10, 2009 6:55 am
Let the ratio be x:9x from statement 1

From second statement
(x/10x)* (x-1)/(10x-1)=3/8 (since both times green ball selected)

we can solve this...

where m i getting ths wrong
Top
Join the discussion
Junior | Next Rank: 30 Posts
Posts: 15
Joined: Sun Nov 11, 2007 9:58 pm
Thanked: 1 times

by aspiregmat » Mon Aug 10, 2009 7:16 am
2) One green ball picked out at fist, the probability that another ball randomly selected is green is 3/8.

It does not say that the probability of picking two green balls is 3/8. It gives the probability of only the second ball.

Even if we take that.... the green and yellow balls will come in fraction which doesn't looks logical. IMO though not sure...
Top
Join the discussion