The Malaysian Indian e-Community

VJeyaa · Last edited by VJeyaa on Mon May 19, 2008 1:30 am; edited 2 times in total

solve this puzzle:

In a country in which people only want boys, every family continues to have children until they have a boy. If they have a girl, they have another child. If they have a boy, they stop. What is the proportion of boys to girls in the country? Assume these are infinite families in the country?
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Before you criticize someone, make sure you walk a mile in their shoes. That way, when you do criticize, you're a mile away and you HAVE THEIR SHOES.

Kon_Roy · Posted: Thu May 08, 2008 12:42 am Post subject: Re: Puzzle #1

Chello · Posted: Thu May 08, 2008 3:31 am Post subject:

if it was 1:0...
how abt the mum's in the country??
arent they included as girls??
if thts the case...
shouldnt it be 1:2
fo every girl...theres two boys..atleast..
the husband and the son
hmm...confusing Confused

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rishi · Senior Member Joined: 06 Mar 2008 Posts: 620

female, male....

2:3 ? Rolling Eyes

tgopal · Junior Member Joined: 17 Mar 2008 Posts: 40

2 : 19

Kon_Roy · Posted: Thu May 08, 2008 11:39 am Post subject:

tgopal · Junior Member Joined: 17 Mar 2008 Posts: 40

Let's wait for the confirmation before opening the champagne bottle

rishi · Senior Member Joined: 06 Mar 2008 Posts: 620

gopal anna...

pls explain how u got the anw

later, nangalum others kittae bantha punnuvom le.. Razz

VJeyaa · Posted: Thu May 08, 2008 12:52 pm Post subject:

Yes, please explain your steps gopal... Wink

_________________
Before you criticize someone, make sure you walk a mile in their shoes. That way, when you do criticize, you're a mile away and you HAVE THEIR SHOES.

tgopal · Junior Member Joined: 17 Mar 2008 Posts: 40

I used excel spreadsheet, assuming a healthy lady gives birth every year for 20 years (quite possible).So, it looks like this :

year B G
1 B 1 0
2 G B 1 1
3 G G B 1 2
4 G G G B 1 3
5 G G G G B 1 4
6 G G G G G B 1 5
7 G G G G G G B 1 6
8 G G G G G G G B 1 7
9 G G G G G G G G B 1 8
10 G G G G G G G G G B 1 9
11 G G G G G G G G G G B 1 10
12 G G G G G G G G G G G B 1 11
13 G G G G G G G G G G G G B 1 12
14 G G G G G G G G G G G G G B 1 13
15 G G G G G G G G G G G G G B 1 14
16 G G G G G G G G G G G G G G G B 1 15
17 G G G G G G G G G G G G G G G G B 1 16
18 G G G G G G G G G G G G G G G G G B 1 17
19 G G G G G G G G G G G G G G G G G G B 1 18
20 G G G G G G G G G G G G G G G G G G G B 1 19
Total 20 190

So, the ratio of boys to girls will be 2:19

VJeyaa · Posted: Fri May 09, 2008 8:13 am Post subject:

Good attempt by Gopal but that is a rather simplistic way of deducing the answer. A woman can probably give birth from her reaching puberty (12?) till she's 45, so it can exceed an assumption of 20 years. Wink

Below is the answer;

Assuming that each time a baby is born the probability it will be a boy is 50% and the probability that it will be a girl is 50%:

The ratio is 1:1

If there are N children born, since the probability that each child be of a particular gender is 1/2, there will probably be N/2 boys and N/2 girls.
_________________
Before you criticize someone, make sure you walk a mile in their shoes. That way, when you do criticize, you're a mile away and you HAVE THEIR SHOES.