Verbal Reasoning - Arithmetic Reasoning - Discussion

Discussion :: Arithmetic Reasoning - Section 1 (Q.No.47)

47. 

In a family, each daughter has the same number of brothers as she has sisters and each son has twice as many sisters as he has brothers. How many sons are there in the family ?

[A]. 2
[B]. 3
[C]. 4
[D]. 5

Answer: Option B

Explanation:

Let d and s represent the number of daughters and sons respectively.

Then, we have :

d - 1 = s and 2 (s - 1) = d.

Solving these two equations, we get: d = 4, s = 3.


Bhavna said: (Aug 28, 2012)  
Please explain.

Parvinder Singh said: (Oct 16, 2014)  
Please tell me how d-1= s and 2 (s-1) = d.

Please explain I can't understand.

Dennydanyanuram said: (Feb 4, 2016)  
d is negative means sister.

s is positive means son.

d - 1 = s as per given data ----> I.

2(s - 1) = d as per given data ----> II.

II in I 2s - 2 - 1 = s.

s = 3 submit in equation I.

d - 1 = 3.

d = 4.

Prashant said: (Feb 21, 2016)  
Please explain the above calculation in detail so, that I can understand it better.

Vampire A said: (Jul 22, 2016)  
Let the number of daughters be d.
Let the number of sons be s.

Case 1:
Daughter has the same number of brothers as she has sisters.
So,
s = d - 1 (because when the daughter is asked , she doesn't count herself) .

Case 2:
Son has twice as many sisters as he has brothers.
So,
2(s-1) = d (because when the son is asked he doesn't count himself).

Solving both the equations.

d = 4 ; s = 3.

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