In my family the females have twice as many sisters as brothers & the males have 5 times as many sisters as brothers. Total males & females = ??

September 11, 2007

Posted by indi

( 1 ratings )

A bit late answer, but just wanted to post the solution how to find the answer :)

Lets introduce next variables:

S - sisters number
B - brothers number

X - number of males
Y - number of females
Z - total males and females

So, first equation is Z = X+Y

2nd equation will be for each female: S/B = 2

Then replace S and B to X and Y to get next equation:
(Y-1)/X = 2

(B = X because the number of males and brothers is the same for female; S = Y-1, because the number of females for concrete female is calculated as all her sisters plus she herself)

3rd equation will be for each male:
S/B = 5

Replacing S and B the same way but relatively to male:
Y/(X-1) = 5

So, now we have equations set of 3:

1. (Y-1)/X = 2
2. Y/(X-1) = 5
3. Z = X+Y

easy to find one of variables, for example,
y = 5 * (x-1)
x = (y-1)/2

x = (5 * (x-1) - 1 ) / 2

x = (5x - 6) / 2

3x = 6

x = 6/3 = 2

Then:
y = 5 * (2 - 1) = 5

z = 7

The same answer as was provided by Charles, but with the solution explanation.. :)

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September 02, 2007

Posted by charles

( 2 ratings )

If we're talking about the children of one nuclear family I think there are a total 7 males and females. 2 x males and 5 x females.

So if I am a male I have one brother and 5 sisters ("5 times as many sisters as brothers"), and if I am a female I have 2 brothers and 4 sisters ("twice as many sisters as brothers").

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