Verbal Reasoning - Arithmetic Reasoning - Discussion

Discussion :: Arithmetic Reasoning - Section 1 (Q.No.21)

21. 

In a class, there are 18 boys who are over 160 cm tall. If these constitute three-fourths of the boys and the total number of boys is two-thirds of the total number of students in the class, what is the number of girls in the class ?

[A]. 6
[B]. 12
[C]. 18
[D]. 24

Answer: Option B

Explanation:

Let the number of boys be x. Then, (3/4)x = 18 or x = 18 x(4/3) = 24.

If total number of students is y, then (2/3) y = 24 or y = 24 x (3/2) = 36.

Therefore Number of girls in the class = (36 - 24) = 12.


Ayush Choudhary said: (Aug 23, 2014)  
I have not understand how to do this help me?

Imran Ali said: (Sep 17, 2014)  
Number of boys in the class say x.

18 are above 160cm and are constitute as 3/4 of the boys, hence
3/4*x = 18 ===> 24.

Total number of student in the class say y.

Total number of boys is 2/3 of the total number of student.
2/3y = 24 ===> y= 36.

Number of girls in the class,
Girls in the class = total student - total boys.
Girls in the class = 36 - 24.
Girls in the class = 12.

Hence answer B is right.

Mohit said: (Jan 15, 2017)  
It's so easy guys.

Let the num of student in class = x.
Then num of boys = 2x/3,
And num of girls = x - 2x/3 = x/3,
Now given that (2x/3)(3/4) = 18,
Hence x = 36.
So, the num of girls = x/3 = 36/3 = 12.

Lakshminarasimha said: (Jul 23, 2018)  
3/4part is boy i.e 18 boys are 160cm.

3*6 = 18, 4*6 = 24.
2/3 part 2 part boys=24,
Girl 1 part =12.

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