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bmwhype2
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Of 200 students, 20% of those who read book A also read book 16 Nov 2007, 06:31
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Of 200 students, 20% of those who read book A also read book B.
25% of those who read book B also read book A.
If each student read at least one of the books, what is the difference between the # of students who read ONLY book A and the # of students who read ONLY book B?

20
25
455
44
46



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Of 200 students, 20% of those who read book A also read book 17 Nov 2007, 05:27
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A+B-AB = 200 ---> only A, only B, both AB

0.2A = 0.25B --> the number of students who read both (i.e AB).

A = 1.25B

A+B-AB = 200

1.25B+B-0.25B = 200

2B = 200

B = 100

A = 125

A-B = 125-100 = 25

the answer is (B)

:)
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Ferihere
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Of 200 students, 20% of those who read book A also read book 17 Nov 2007, 06:17
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KillerSquirrel
A+B-AB = 200 ---> only A, only B, both AB

0.2A = 0.25B --> the number of students who read both (i.e AB).

A = 1.25B

A+B-AB = 200

1.25B+B-0.25B = 200

2B = 200

B = 100

A = 125

A-B = 125-100 = 25

the answer is (B)

:)
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the same B and answer 25
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Of 200 students, 20% of those who read book A also read book 17 Nov 2007, 10:02
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how do you get AB = 0.25B ?
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KillerSquirrel
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Of 200 students, 20% of those who read book A also read book 17 Nov 2007, 10:07
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pmenon
how do you get AB = 0.25B ?
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Of 200 students, 20% of those who read book A also read book B.
25% of those who read book B also read book A. If each student read at least one of the books, what is the difference between the # of students who read ONLY book A and the # of students who read ONLY book B?

:)
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Of 200 students, 20% of those who read book A also read book 17 Nov 2007, 10:11
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KillerSquirrel
pmenon
how do you get AB = 0.25B ?

Of 200 students, 20% of those who read book A also read book B.
25% of those who read book B also read book A. If each student read at least one of the books, what is the difference between the # of students who read ONLY book A and the # of students who read ONLY book B?

:)
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wow, i cant believe i missed this. This is why i dont do well on quant !
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Himalayan
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Of 200 students, 20% of those who read book A also read book 17 Nov 2007, 10:40
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bmwhype2
Of 200 students, 20% of those who read book A also read book B. 25% of those who read book B also read book A. If each student read at least one of the books, what is the difference between the # of students who read ONLY book A and the # of students who read ONLY book B?

20
25
455
44
46
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0.2a=0.25b
4a = 5b

a + b - ab = 200
or, only a + only b + ab = 200
0.8a + 0.75b + 0.2a = 200
0.8a + 0.75(4a/5) + 0.2a = 200
0.8a + 0.75(4a/5) + 0.2a = 200
8a = 5x200
a = 125
b = 4a/5 = 4x125/5 = 100
a-b = 125 - 100 = 25
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Of 200 students, 20% of those who read book A also read book 17 Nov 2007, 16:17
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Even though OA is B, question asked for Only A - Only B
Seems like everyone missed that.

Now Only A = 125 - 25 = 100 and Only B = 100 - 25 = 75
and the difference is 25 that is same as choice B.
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KillerSquirrel
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Of 200 students, 20% of those who read book A also read book 17 Nov 2007, 22:26
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gk2k2
Even though OA is B, question asked for Only A - Only B
Seems like everyone missed that.

Now Only A = 125 - 25 = 100 and Only B = 100 - 25 = 75
and the difference is 25 that is same as choice B.
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Agree !

:)
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Of 200 students, 20% of those who read book A also read book 17 Nov 2007, 22:49
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One can use drawing:

A,B,AB present equal quantity of students.

A
A
A
A
(AB) B B B

8 (AB) = 200

AB=25
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jimmyjamesdonkey
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Of 200 students, 20% of those who read book A also read book Updated on: 18 Nov 2007, 15:11
Originally posted by jimmyjamesdonkey on 18 Nov 2007, 15:10.
Last edited by jimmyjamesdonkey on 18 Nov 2007, 15:11, edited 1 time in total.
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KillerSquirrel
A+B-AB = 200 ---> only A, only B, both AB
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0.2A = 0.25B --> the number of students who read both (i.e AB).

A = 1.25B

A+B-AB = 200

1.25B+B-0.25B = 200

I'm missing this -AB part. How are you getting the .25 from the problem? I thought A = 1.25B as stated above.
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jimmyjamesdonkey
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Of 200 students, 20% of those who read book A also read book 18 Nov 2007, 15:13
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Don't see how you are getting the values for Set 1,2,3. Please elaborate.
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KillerSquirrel
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Of 200 students, 20% of those who read book A also read book 18 Nov 2007, 15:18
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jimmyjamesdonkey
KillerSquirrel
A+B-AB = 200 ---> only A, only B, both AB

0.2A = 0.25B --> the number of students who read both (i.e AB).

A = 1.25B

A+B-AB = 200

1.25B+B-0.25B = 200

I'm missing this -AB part. How are you getting the .25 from the problem? I thought A = 1.25B as stated above.
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AB = 0.25B
AB = 0.2A

hence:

0.25B = 0.2A

:)



Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Quantitative Questions Forum
Still interested in this question? Check out the "Best Topics" block above for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!