BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem
TTP OnDemand GMAT Video Course
Featured Course

Target Test Prep GMAT OnDemand

Scott Woodbury-Stewart’s private virtual classroom — 400 hours of master-class video lessons for the GMAT Focus Edition.

  • 715+ score guarantee — highest in the industry (99th percentile)
  • 52 chapters · 1,500+ lessons · 4,000+ practice questions
  • 400 hours of video · 1,500+ instructor-led HD smartboard lessons
  • 300,000+ students accepted to Harvard, Stanford, Wharton, Booth & Sloan & more
  • 24/7 live support + weekly Zoom office hours with GMAT instructors
  • TTP AI Assist — 24/7 AI-powered virtual tutor for instant help
  • 1,200+ flashcards + AI-powered study assistant & daily calendar
  • OnDemand, LiveTeach & GMAT Bootcamp formats available
  • Also: GRE, SAT Math & Executive Assessment courses
  • MBA Admissions Consulting now available
  • 🏆 2025 EdTech Breakthrough Award: Test Prep Solution Provider of the Year
  • 200,000+ students served
  • 5-day free trial — $0 to start, no auto-billing, cancel anytime
★★★★★ 5.0 (559 reviews)
130-pt guarantee
$0 to start then $127/mo
Start Free 5-Day Trial Read 559 Reviews →

probability

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Junior | Next Rank: 30 Posts
Posts: 11
Joined: Mon Mar 30, 2009 10:11 am
by rickjan » Sun Nov 15, 2009 6:17 am
if the probability that event A will occur is 0.5 what's the probability that event B will occur?

1) the probability that both A and B will occur is 0.3
2) the probability that at least one of the events will occur is 0.8
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Data Sufficiency |
Master | Next Rank: 500 Posts
Posts: 138
Joined: Mon Mar 02, 2009 12:02 pm
Thanked: 15 times

by life is a test » Sun Nov 15, 2009 6:31 pm
rickjan wrote:if the probability that event A will occur is 0.5 what's the probability that event B will occur?

1) the probability that both A and B will occur is 0.3
2) the probability that at least one of the events will occur is 0.8
IMO D

1. p(a) * p(b) = 0.3 -> 0.5 * p(b) = 0.3 -> suff
2. p(a) + p(b) + p(ab) = 0.8 = 0.5 + p(b) + 0.5*p(b) -> suff.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
GMAT Instructor
Posts: 3225
Joined: Tue Jan 08, 2008 2:40 pmFollowed by: 614 members
Location: Toronto
Thanked: 1710 times
GMAT Score:800

by Stuart@KaplanGMAT » Sun Nov 15, 2009 7:55 pm
rickjan wrote:if the probability that event A will occur is 0.5 what's the probability that event B will occur?

1) the probability that both A and B will occur is 0.3
2) the probability that at least one of the events will occur is 0.8
Where's the question from? Did you copy it verbatim?

I'm sure that D is the intended answer to the question - but in order for either statement to be useful, we need to know that A and B are independent events.
Image

Stuart Kovinsky | Kaplan GMAT Faculty | Toronto

Kaplan Exclusive: The Official Test Day Experience | Ready to Take a Free Practice Test? | Kaplan/Beat the GMAT Member Discount
BTG100 for $100 off a full course
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 371
Joined: Fri Mar 06, 2009 2:48 am
Thanked: 27 times
GMAT Score:740

by 2010gmat » Fri Nov 20, 2009 6:57 am
Stuart when you say D is the intended answer...does it mean that its a trap or does it mean that D is the right answer
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
GMAT Instructor
Posts: 3225
Joined: Tue Jan 08, 2008 2:40 pmFollowed by: 614 members
Location: Toronto
Thanked: 1710 times
GMAT Score:800

by Stuart@KaplanGMAT » Fri Nov 20, 2009 7:52 am
2010gmat wrote:Stuart when you say D is the intended answer...does it mean that its a trap or does it mean that D is the right answer
It means that I think the question is worded very poorly; in its current form the answer should be E (not enough information), but my guess it that whoever wrote the question intended each statement to be sufficient alone.
Image

Stuart Kovinsky | Kaplan GMAT Faculty | Toronto

Kaplan Exclusive: The Official Test Day Experience | Ready to Take a Free Practice Test? | Kaplan/Beat the GMAT Member Discount
BTG100 for $100 off a full course
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1