Puzzle: Country of boys!!!

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In a country where people only want boys, every family continues to have children until they have a boy. if they have a girl, they go for another child. if they have a boy, they stop. what is the proportion of boys to girls in the country?
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Sangeeta Haldhar Sangeeta Haldhar   11 years ago

1:1

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Sangeeta Haldhar Sangeeta Haldhar   11 years ago

Kind ofsum of infinite GP
a/(1-r)

1:1

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Sangeeta Haldhar Sangeeta Haldhar   11 years ago

How the ratio comes to be 1:1 by using a/(1-r) ??

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Deepak Aggarwal Deepak Aggarwal   10 years ago

1:1

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Rajat Kumar Rajat Kumar   10 years ago

Ans.

Reason: girl boys
0 1
1 1
2 1
: :
: :
N 1

sum: N(N+1)/2 N+1

boys:girl 2:N or 1:N-1

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