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In a class of a school, there were 40 percent boys. If some of the stu

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In a class of a school, there were 40 percent boys. If some of the stu  [#permalink]

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New post 24 Sep 2018, 05:30
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In a class of a school, there were 40 percent boys. If some of the students were transferred to a new section and 30 percent of the transferred students were boys, what was the ratio of the transfer rate for the boys to the transfer rate for the girls?

(A) 1 : 4
(B) 2 : 7
(C) 4 : 9
(D) 9 : 14
(E) 9 : 16

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Re: In a class of a school, there were 40 percent boys. If some of the stu  [#permalink]

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New post 24 Sep 2018, 08:34
Bunuel wrote:
In a class of a school, there were 40 percent boys. If some of the students were transferred to a new section and 30 percent of the transferred students were boys, what was the ratio of the transfer rate for the boys to the transfer rate for the girls?

(A) 1 : 4
(B) 2 : 7
(C) 4 : 9
(D) 9 : 14
(E) 9 : 16


Boys % = 40 ==> Girls% =60
Transferred Boys % =30 ==>Transferred Girls % =70
Hence, Transferred Boys wrt total students % = 40 * 30 & Similarly , Transferred Girls wrt total students % = 60 * 70
Therefore , TB:TG = 40 * 30 : 60 * 70 = 2:7.........Answer B
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Re: In a class of a school, there were 40 percent boys. If some of the stu  [#permalink]

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New post 25 Sep 2018, 02:45
Number of Students = 100 ; Boys = 40 ; Girls = 60.
X students were transferred ; 0.3x were boys ; 0.7x were girls
Ratio of transfer rate of boys to girl =[ 0.3x/40 ] / [0.7x/60] = 9 : 14
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Re: In a class of a school, there were 40 percent boys. If some of the stu  [#permalink]

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New post 25 Sep 2018, 03:04
Let the total number of students be 100
40% boys=40
60% girls=60

Transferred to new section
30/100x40 = 12 Boys
70/100x60 = 42 girls

New Ratio = Boys/girls = 12/42 =2:7

IMO B

But why is OA D?

Am I doing something wrong or the OA is incorrect?
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Re: In a class of a school, there were 40 percent boys. If some of the stu  [#permalink]

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New post 25 Sep 2018, 03:08
pandeyashwin wrote:
Number of Students = 100 ; Boys = 40 ; Girls = 60.
X students were transferred ; 0.3x were boys ; 0.7x were girls
Ratio of transfer rate of boys to girl =[ 0.3x/40 ] / [0.7x/60] = 9 : 14


How did you get 9:14? Could you please explain it?
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Re: In a class of a school, there were 40 percent boys. If some of the stu  [#permalink]

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New post 25 Sep 2018, 03:35
3
Bunuel wrote:
In a class of a school, there were 40 percent boys. If some of the students were transferred to a new section and 30 percent of the transferred students were boys, what was the ratio of the transfer rate for the boys to the transfer rate for the girls?

(A) 1 : 4
(B) 2 : 7
(C) 4 : 9
(D) 9 : 14
(E) 9 : 16


Say there were 40 boys and 60 girls.
Say 10 students were transferred such that 3 boys and 7 girls were transferred.

Transfer rate of boys = 3/40
Transfer rate of girls = 7/60

Required Ratio = (3/40) / (7/60) = 9:14
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Re: In a class of a school, there were 40 percent boys. If some of the stu  [#permalink]

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New post 25 Sep 2018, 06:56
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ArjunJag1328 wrote:
Let the total number of students be 100
40% boys=40
60% girls=60

Transferred to new section
30/100x40 = 12 Boys
70/100x60 = 42 girls

New Ratio = Boys/girls = 12/42 =2:7

IMO B

But why is OA D?

Am I doing something wrong or the OA is incorrect?

Hey ,
The question says "30 percent of the transferred students were boys" , not "30% of the boys were transferred"
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Re: In a class of a school, there were 40 percent boys. If some of the stu   [#permalink] 25 Sep 2018, 06:56
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