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GeekInterview.com > Placement Papers > Aalayance Inc
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Question: In one country they prefer only boys to have. If it is a girl in the
first birth then there must be the other child to have,
if it is also a girl then they will go for the next birth and stops when
they got the boy. Then what is the proportion of
girl to boys in that country?
Answer: (n+1)/2:1 |
| September 09, 2007 15:44:32 |
#2 |
| Abhiram Kasina |
Member Since: Visitor Total Comments: N/A |
RE: In one country they prefer only boys to have. If i...
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Its a standard probability question
Let r = boys:girls ratio
P(having 1 boy 1 girl) = P(girl in first attempt)P(boy in the second)
= 0.5*0.5
= P(r=1)
P(2 girls, 1 boy) = P(girl in first attempt)P(girl in second attempt)P(boy in the third)
= 0.5*0.5*0.5
= P(r=2)
generalising...
P(r=n) = (.5)^(n+1) ^ stands for exponent
Expected value of r is given by
Integral (n((.5)^(n+1))) dn
Limits 0 to inf
which evaluates to 2.081368981005607797869581603735
So girls are almost double in number than boys
leave it if its too complex...
& @ Studs do drop in a mail if I am mistaken somewhere |
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