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@rengaraj • 07 Nov, 2009
Sir / madam,
My question is

A family I know has several children. Each boy in this family has as many sisters as brothers but each girl has twice as many brothers as sisters. How many brothers and sisters are there?

Advance Thanks,
{SCE 34/2008/Pg 4 of 85}
{On this forum my 4th Question.}
@yadavundertaker mohit • 07 Nov, 2009 1 sister and 2 brothers.
@rengaraj • 08 Nov, 2009
1 sister and 2 brothers.
Can it be 2 sister and 4 brother ???
Since they specified as many sisters.
Please Suggest.
@yadavundertaker mohit • 08 Nov, 2009 what i think is that the question is not correct or i am unable to get it ...lets try it mathematically step by step

Let no. of brothers =x

Let no. of sisters =y

Acc. to Ist condition


Acc. to 2nd condition


putting value of x in 2nd from Ist


y=-3 which is not possible

then value of x is = -2 again it is not possible ...
@yadavundertaker mohit • 08 Nov, 2009 if the 2nd condition means each sister has double the sister as many as brother then we can solve this question

then 2nd condition becomes

2(y-1)= x

putting value of x from Ist equation to 2nd

2(y-1) =y+1

y= 3

then x = 4

No. of brothers =4

No. of sisters =3
@yadavundertaker mohit • 08 Nov, 2009
Can it be 2 sister and 4 brother ???
Since they specified as many sisters.
Please Suggest.

there cann't be 2 sisters if there are 4 brothers because according to the Ist each brother has same no. of sisters and brothers .And acc. to your answer each brother has 3 brothers and 2 sisters....
@Saandeep Sreerambatla • 09 Nov, 2009 The answer should be 3 sisters and 4 brothers.

Cond1 - Each brother has as many sisters as brothers.

So considering s1,s2,s3 and b1, b2,b3 and b4
Each of the b1 to b4 has 3 sisters and 3 brothers.

Cond2- Each girl has twice as many brothers as sisters

So now s1 has 2 sisters and 4 brothers.

similarly s2 and s3 also.

The answer is 3s and 4b..

Its not 1s and 2b because according to second condition there should be more than 1 girl.
@rengaraj • 09 Nov, 2009 Sir,
Excellent answer given.
But i didn't try mathematically, that's my mistake.
@sharadha Shivakumar • 28 Oct, 2018

sir is it ok  to use co prime numbers

@Karshil Sheth • 14 Feb, 2020

I am guessing it randomly according to given situation.

So let be sisters be G and Brothers be B.

If There are 7 children, & G =2B, then for each girl there can be 4 brothers and 3 sisters.

so S1=B1,B2

 S2= B2,B3


So I guess answer is :3 sisters and 4 brothers.

@Divisha Madupalli • 14 Feb, 2020

no of boys is higher than girls by 1

 it is only possible when she has 2 sisters and 4 bothers.

Answer is: There are 4 sons and 3 daughters.


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