Union of three sets formula derivation? : Ask GMAT Experts
Check GMAT Club Decision Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 17 Jan 2017, 08:43

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Union of three sets formula derivation?

Author Message
Joined: 31 Dec 1969
Location: Russian Federation
Concentration: Technology, Entrepreneurship
GMAT 1: 710 Q49 V0
GMAT 2: 700 Q V
GMAT 3: 740 Q40 V50
GMAT 4: 700 Q48 V38
GMAT 5: 710 Q45 V41
GMAT 6: 680 Q47 V36
GMAT 7: Q42 V44
GMAT 8: Q42 V44
GMAT 9: 740 Q49 V42
GMAT 10: 740 Q V
GMAT 11: 500 Q47 V33
GMAT 12: 670 Q V
WE: Engineering (Manufacturing)
Followers: 0

Kudos [?]: 199 [0], given: 102152

Union of three sets formula derivation? [#permalink]

### Show Tags

10 Jan 2012, 17:20
okay so i know the formula for this is:
P(A) + P(B) + P(C) - P(AnB) - P(AnC) - P(BnC) + P(AnBnC)
but i literally do not understand how to get the P(AnBnC)
can someone please beak it down for me ?
Kaplan GMAT Instructor
Joined: 25 Aug 2009
Posts: 644
Location: Cambridge, MA
Followers: 83

Kudos [?]: 276 [1] , given: 2

Re: Union of three sets formula derivation? [#permalink]

### Show Tags

10 Jan 2012, 19:10
1
KUDOS
Expert's post
Let's suppose an object X is in A, B, and C.

Since you are counting A, B, and C serparately, you've counted X three times.

But then, you subtract everything in A & B, B & C, and A & C. X is in each of those, so you've subtracted X three times. That means you haven't actually counted X.

So, you need to add X (and every other object in A, B, and C) to get the correct total, because otherwise you aren't counting it.
_________________

Eli Meyer
Kaplan Teacher
http://www.kaptest.com/GMAT

Prepare with Kaplan and save \$150 on a course!

Kaplan Reviews

Re: Union of three sets formula derivation?   [#permalink] 10 Jan 2012, 19:10
Similar topics Replies Last post
Similar
Topics:
5 What is Test set? 1 24 Oct 2014, 01:31
Equations for 3 overlapping sets 1 21 Jun 2013, 20:28
Issues with Overlapping sets 1 12 Aug 2012, 03:01
Questions on overalpping sets & geometry 0 25 Nov 2011, 17:41
Taking derivatives on GMAT questions 2 14 Nov 2011, 10:55
Display posts from previous: Sort by