• Target Test Prep
    5-Day Free Trial
    5-day free, full-access trial TTP Quant

    Available with Beat the GMAT members only code

    MORE DETAILS
    Target Test Prep
  • Varsity Tutors
    Award-winning private GMAT tutoring
    Register now and save up to $200

    Available with Beat the GMAT members only code

    MORE DETAILS
    Varsity Tutors
  • e-gmat Exclusive Offer
    Get 300+ Practice Questions
    25 Video lessons and 6 Webinars for FREE

    Available with Beat the GMAT members only code

    MORE DETAILS
    e-gmat Exclusive Offer
  • Veritas Prep
    Free Veritas GMAT Class
    Experience Lesson 1 Live Free

    Available with Beat the GMAT members only code

    MORE DETAILS
    Veritas Prep
  • PrepScholar GMAT
    5 Day FREE Trial
    Study Smarter, Not Harder

    Available with Beat the GMAT members only code

    MORE DETAILS
    PrepScholar GMAT
  • Economist Test Prep
    Free Trial & Practice Exam
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    Economist Test Prep
  • EMPOWERgmat Slider
    1 Hour Free
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    EMPOWERgmat Slider
  • Kaplan Test Prep
    Free Practice Test & Review
    How would you score if you took the GMAT

    Available with Beat the GMAT members only code

    MORE DETAILS
    Kaplan Test Prep
  • Magoosh
    Magoosh
    Study with Magoosh GMAT prep

    Available with Beat the GMAT members only code

    MORE DETAILS
    Magoosh
  • examPAL
    Most awarded test prep in the world
    Now free for 30 days

    Available with Beat the GMAT members only code

    MORE DETAILS
    examPAL

Arithmetic Probability

This topic has 6 member replies
dheaven1 Junior | Next Rank: 30 Posts Default Avatar
Joined
08 Feb 2010
Posted:
10 messages

Arithmetic Probability

Post Thu Feb 18, 2010 11:18 pm
Among a group of 2,500 people, 35 percent invest in
municipal bonds, 18 percent invest in oil stocks, and
7 percent invest in both municipal bonds and oil
stocks. If 1 person is to be randomly selected from
the 2,500 people, what is the probability that the
person selected will be one who invests in municipal
bonds but NOT in oil stocks?

A. 9/50
B. 7/25
C. 7/20
D. 21/50
E. 27/50


I need explanation on why you would factor in the 7 percent invested in both municipal bonds and oil stocks.

  • +1 Upvote Post
  • Quote
  • Flag
garavkaram Newbie | Next Rank: 10 Posts
Joined
16 Nov 2010
Posted:
1 messages
Post Tue Nov 16, 2010 6:42 am
Hi Experts, help me pls.

here's what I am stuck at:-

1.) person who invested in oil stocks = 18%
1.a) person who NOT invested in oil stocks = (100-18) = 82%
2.) person who invetsed in municipal bond = 35 %

combining 1.a. & 2 we get,
person invested in municipal bond AND NOT in oil stock = 82% * 35 % which is not 7/25.

I am sure I am missing something but dont know what..

Would appreciate your support.

regards,

  • +1 Upvote Post
  • Quote
  • Flag
Fractal Master | Next Rank: 500 Posts Default Avatar
Joined
22 Aug 2010
Posted:
183 messages
Upvotes:
5
Test Date:
24.09.2011
Target GMAT Score:
700
Post Sun Jul 31, 2011 9:17 am
ajith wrote:
dheaven1 wrote:
Among a group of 2,500 people, 35 percent invest in
municipal bonds, 18 percent invest in oil stocks, and
7 percent invest in both municipal bonds and oil
stocks. If 1 person is to be randomly selected from
the 2,500 people, what is the probability that the
person selected will be one who invests in municipal
bonds but NOT in oil stocks?

A. 9/50
B. 7/25
C. 7/20
D. 21/50
E. 27/50


I need explanation on why you would factor in the 7 percent invested in both municipal bonds and oil stocks.
35 percent invests in municipal bonds this includes the 7% who invested in both municipal bonds and oil stocks.

So 28 percent invests in municipal bonds but not in oil stocks

Now the probability is 28/100 = 7/25
wow, what an easy way! it takes like 15 seconds to solve the question like this! i didn't recognize that unfortunately and hence draw a double-matrix, which costs me some seconds...

  • +1 Upvote Post
  • Quote
  • Flag
thephoenix Legendary Member
Joined
17 Nov 2009
Posted:
1560 messages
Followed by:
4 members
Upvotes:
137
Target GMAT Score:
750
Post Thu Feb 18, 2010 11:46 pm
dheaven1 wrote:
Among a group of 2,500 people, 35 percent invest in
municipal bonds, 18 percent invest in oil stocks, and
7 percent invest in both municipal bonds and oil
stocks. If 1 person is to be randomly selected from
the 2,500 people, what is the probability that the
person selected will be one who invests in municipal
bonds but NOT in oil stocks?

A. 9/50
B. 7/25
C. 7/20
D. 21/50
E. 27/50


I need explanation on why you would factor in the 7 percent invested in both municipal bonds and oil stocks.
imO b

IF U USE DOUBLE MATRIX SYS OF mgmat

U WILL GET THE NO OF PEPOLE WHO INVEST IN BOND AND NOT OIL STOCK=28*25

PROB=28*25/2500=7/25

  • +1 Upvote Post
  • Quote
  • Flag
ajith Legendary Member
Joined
21 Sep 2006
Posted:
1275 messages
Followed by:
2 members
Upvotes:
125
Test Date:
April 2010
Target GMAT Score:
740
Post Thu Feb 18, 2010 11:49 pm
dheaven1 wrote:
Among a group of 2,500 people, 35 percent invest in
municipal bonds, 18 percent invest in oil stocks, and
7 percent invest in both municipal bonds and oil
stocks. If 1 person is to be randomly selected from
the 2,500 people, what is the probability that the
person selected will be one who invests in municipal
bonds but NOT in oil stocks?

A. 9/50
B. 7/25
C. 7/20
D. 21/50
E. 27/50


I need explanation on why you would factor in the 7 percent invested in both municipal bonds and oil stocks.
35 percent invests in municipal bonds this includes the 7% who invested in both municipal bonds and oil stocks.

So 28 percent invests in municipal bonds but not in oil stocks

Now the probability is 28/100 = 7/25

_________________
Always borrow money from a pessimist, he doesn't expect to be paid back.

  • +1 Upvote Post
  • Quote
  • Flag
harsh.champ Legendary Member
Joined
20 Jul 2009
Posted:
1132 messages
Followed by:
6 members
Upvotes:
64
Test Date:
30/03/2012
Target GMAT Score:
780+
GMAT Score:
760
Post Fri Feb 19, 2010 12:07 am
dheaven1 wrote:
Among a group of 2,500 people, 35 percent invest in
municipal bonds, 18 percent invest in oil stocks, and
7 percent invest in both municipal bonds and oil
stocks. If 1 person is to be randomly selected from
the 2,500 people, what is the probability that the
person selected will be one who invests in municipal
bonds but NOT in oil stocks?

A. 9/50
B. 7/25
C. 7/20
D. 21/50
E. 27/50


I need explanation on why you would factor in the 7 percent invested in both municipal bonds and oil stocks.
Hey dheaven1,
If you are having problems with such type of questions,you should try doing them using Venn-Diagrams.
It will seem very easy when you have the diagram by your side.
In probability,I have found Venn-Diagram to be very useful for advanced problems.
Also,You should consult set theory side by side.


As for the question it can be solved using the equation:-
P(A U B) = P(A) + P(B) - P(A n B) [U-union, n -intersection]

In the question,we have to find P(B) - P(A n B)

_________________
It takes time and effort to explain, so if my comment helped you please press Thanks button Smile



Just because something is hard doesn't mean you shouldn't try,it means you should just try harder.

"Keep Walking" - Johnny Walker Razz

  • +1 Upvote Post
  • Quote
  • Flag
shashank.ism Legendary Member
Joined
20 Jul 2009
Posted:
1021 messages
Followed by:
2 members
Upvotes:
41
Test Date:
ND
Target GMAT Score:
780
GMAT Score:
NA
Post Sun Feb 21, 2010 3:34 pm
dheaven1 wrote:
Among a group of 2,500 people, 35 percent invest in
municipal bonds, 18 percent invest in oil stocks, and
7 percent invest in both municipal bonds and oil
stocks. If 1 person is to be randomly selected from
the 2,500 people, what is the probability that the
person selected will be one who invests in municipal
bonds but NOT in oil stocks?

A. 9/50
B. 7/25
C. 7/20
D. 21/50
E. 27/50


I need explanation on why you would factor in the 7 percent invested in both municipal bonds and oil stocks.
%ge \invested in mutual bond = 35 m

person who invetsed in mutual bond = 35 %
person who invested in oil stocks = 18%
person who invested in bopt h = 7%
person who invested in mutual bond and not oil stocks= 35 -7 = 28

so %ge = 28 /100 = 7 /25 Ans B

_________________
My Websites:
http://mba.webmaggu.com - India's social Network for MBA Aspirants

http://deal.webmaggu.com -India's online discount, coupon, free stuff informer.

http://dictionary.webmaggu.com - A compact free online dictionary with images.

Nothing is Impossible, even Impossible says I'm possible.

  • +1 Upvote Post
  • Quote
  • Flag

Best Conversation Starters

1 lheiannie07 112 topics
2 ardz24 71 topics
3 Roland2rule 69 topics
4 LUANDATO 53 topics
5 swerve 45 topics
See More Top Beat The GMAT Members...

Most Active Experts

1 image description GMATGuruNY

The Princeton Review Teacher

154 posts
2 image description Rich.C@EMPOWERgma...

EMPOWERgmat

107 posts
3 image description Jeff@TargetTestPrep

Target Test Prep

106 posts
4 image description Scott@TargetTestPrep

Target Test Prep

98 posts
5 image description EconomistGMATTutor

The Economist GMAT Tutor

91 posts
See More Top Beat The GMAT Experts