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In a class, teacher decides to choose two students for a certain exper

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amanvermagmat
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In a class, teacher decides to choose two students for a certain exper [#permalink] New post   05 Jun 2018, 11:56
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In a class, teacher decides to choose two students for a certain experiment, out of the boys and girls present. In how many ways can the teacher choose two boys for the same?

(1) Number of boys is 20% less than the number of girls in the class.

(2) Number of girls is 3 more than the number of boys in the class.
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rakeshmishra5690
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Re: In a class, teacher decides to choose two students for a certain exper [#permalink] New post   05 Jun 2018, 12:09
IMO ans is C

We need to find number of boys.

Let number of boys = B
number of girls = G

As we need to select 2 boys so number of ways = BC2

1) B = 0.8G . not sufficient as there will me infinite number of values satisfying this equation

2) G = B + 3. not sufficient. again infinite solution

1) +2)

G = 0.8G + 3
G = 15
B = 13

hence number of ways 13C2

Ans C
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In a class, teacher decides to choose two students for a certain exper [#permalink] New post   06 Jun 2018, 01:16
amanvermagmat wrote:
In a class, teacher decides to choose two students for a certain experiment, out of the boys and girls present. In how many ways can the teacher choose two boys for the same?

(1) Number of boys is 20% less than the number of girls in the class.

(2) Number of girls is 3 more than the number of boys in the class.



1. Number of boys is 20% less than the number of girls in the class.
We don't know the total number of boys/girls in the class. Without this
information, we cannot find how many ways can two boys be chosen (Insufficient)

2. Number of girls is 3 more than the number of boys in the class.
We don't know the total number of boys/girls in the class. Without this
information, we cannot find how many ways can two boys be chosen (Insufficient)

When we combine the information in both the statements,
we know 0.2(#Girls) = 3 -> #Girls = 15. Now, #Boys = 12
The total ways in which a teacher can choose two boys is \(C_2^{12} = 66\) (Sufficient - Option C)
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Re: In a class, teacher decides to choose two students for a certain exper [#permalink] New post   11 Jul 2019, 00:02
rakeshmishra5690 wrote:
IMO ans is C

We need to find number of boys.

Let number of boys = B
number of girls = G

As we need to select 2 boys so number of ways = BC2

1) B = 0.8G . not sufficient as there will me infinite number of values satisfying this equation

2) G = B + 3. not sufficient. again infinite solution

1) +2)

G = 0.8G + 3
G = 15
B = 13

hence number of ways 13C2

Ans C


Hey! The number of boys would be 12, not 13.
Thus the number of ways would be 12C2 and not 13C2.

Answer remains C though!
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Re: In a class, teacher decides to choose two students for a certain exper [#permalink] New post   14 Apr 2024, 06:51
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Re: In a class, teacher decides to choose two students for a certain exper [#permalink]
14 Apr 2024, 06:51
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