Family Ties
Boy says: "I have as many brothers as sisters."
His sister says, "I have twice as many brothers as sisters."
How many of brothers and sisters are there in the family ?
Labels: logic
posted by ToM at
4:48 AM
10 Comments:
4 brothers and 3 sisters
3 sister and 4 Brothers.
X = #Sisters
X+1 = #Broters
1+2X= 2(X-1) + X
42!!!
i say 2 brothers and 2 sisters, because he says he has as many brothers as he has sisters so 2=2 and she said she has twice as many brothers as she has sisters wich is 2 brothers = 1 sister (because she is not counting her self, like the brother did
I doubt that either the brother or sister included themselves.
As I am one of 4 brothers, I would say that I have 3 brothers.
So #brothers-1 = #sisters
and #brothers = 2*(#sisters-1)
Let b = #brothers, s = #sisters
So b-1 = s => b = s+1
and b = 2(s-1) = s+1 (using above)
so 2s-2 = s+1 => s=3 => b=4
So there are 4 brothers and 3 sisters.
If the brother and sister did include themselves, then at least one of them has a mistake in their information.
well its obvious that they cannot include themselves:S..the solution is 4 boys 3 girls
duh.... I believe the answer is 3 two boys and one girl, the boy speaking has one brother and one sister and the sister has two brothers and no sisters (twice as many)
If it was two brothers and one sister altogether, the the sister would have said I have infinitely many more brothers than sisters because she wouldn't have any sisters.
....or if the only sister still insisted that she had twice as many brothers as sisters, that would mean she has 2*0 = 0 brothers. So the first boy is a figment of our imagination.
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