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

OG 12 - Probability

Problem Solving — algebra and arithmetic
Expert replies
Post new topic Post Reply
Subscribe topic
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 40
Joined: Mon Feb 16, 2009 8:50 pm
Thanked: 3 times
by crackthetest » Sat Feb 27, 2010 1:26 pm
On page 118,

" E or F " is the set of outcomes in E or F or both.
" E and F " is the set of outcomes in both E and F.

But P(E or F) = P(E) + P(F) - P(E and F).

I know by additional rule that this is case,
shouldn't "E or F" state " is the set of outcomes in E or F and not both "?
Top
Join the discussion
Source: — Quantitative Reasoning |
Junior | Next Rank: 30 Posts
Posts: 25
Joined: Wed Sep 02, 2009 1:52 pm
Thanked: 4 times

by kelsi111 » Sun Feb 28, 2010 8:47 am
This comes down to Math talk not exactly mapping to English talk. What you are referring to in
Shouldn't "E or F" state " is the set of outcomes in E or F and not both "?
is called an XOR which is different from OR. I don't know if XOR will be on the GMAT.

OR means that the answer is in either set and doesn't count the middle twice as you would if you just added the two probabilities: P( e OR f ) = P(e) + P(f) - P(e AND f) as you have stated.

An item being in either but not both as you have described is an XOR. P( e XOR f ) = P( e OR f ) - P( e AND f ) = P(e) + P(f) - 2 ( P(e AND f) ).
Top
Join the discussion