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Arithmetic Probability

by dheaven1 » Thu Feb 18, 2010 11:18 pm

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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.
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by thephoenix » 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
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by ajith » 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
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by harsh.champ » 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 :)



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by shashank.ism » 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 = [spoiler]7 /25 Ans B [/spoiler]
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by garavkaram » 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,
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by Fractal » 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...
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by [email protected] » Tue Apr 10, 2018 11:25 am
Hi All,

We're told that 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. We're asked 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.

This question is a variation on an Overlapping Sets question, so it can be solved in a couple of different ways. Regardless of how you choose to approach the work, you will have to account for the fact that the people who invested in BOTH bonds and stocks were 'counted twice.' The 7% of the people who invested in BOTH bonds and stocks appear as part of the 35% who invested in bonds AND in the 18% who invested in stocks. Thus, you can 'work backwards' and determine the percentage of people who invested in just ONE of those choices:

BOTH bonds & stocks = 7%
Bonds = 35% - 7% = 28% of the people invested in JUST bonds
Stocks = 18% - 7% = 11% of the people invested in JUST stocks

Thus, the probability of selecting someone from the group who invested in JUST bonds = 28% = 7/25

Final Answer: B

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by Scott@TargetTestPrep » Thu Apr 12, 2018 3:52 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
The number of people who invest in ONLY municipal bonds is:

2,500 x 0.35 - 2,500 x 0.07

2,500(0.35 - 0.07) = 2,500(0.28) = 700

So, the probability that the person selected will be one who invests in municipal bonds and NOT in oil stocks is 700/2500 = 7/25.

Answer: B

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by palgun » Tue Sep 03, 2019 11:27 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.
It is easier to explain using venn dia of 2 circles. 7% would be those investing in both so they are unique people other than those investing individually.
Hope this helps
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