Arithmetic Probability

Question

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.

thephoenix · Answer

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)

ajith · Answer

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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harsh.champ · Answer

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

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

"Keep Walking" - Johnny Walker

shashank.ism · Answer

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

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

"Keep Walking" - Johnny Walker

garavkaram · Answer

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,

Fractal · Answer

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...

Rich.C@EMPOWERgmat.com · Answer

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

GMAT assassins aren't born, they're made,
Rich

Contact Rich at [email protected]

Scott@TargetTestPrep · Answer

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)

palgun · Answer

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]

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

www.deal.webmaggu.com -India's online discount, coupon, free stuff informer.

www.dictionary.webmaggu.com - A compact free online dictionary with images.

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

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