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Mr. Wong has 10 grandchildren. Assuming that the gender of each child is determined independently and with equal likelihood of male and female, what is the probability that Mr. Wong has more grandsons than granddaughters or more granddaughters than grandsons?

 Jan 5, 2017

Best Answer 

 #2
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+10

1) Equal probability of 5 boys and 5 boys =

 

binomial(5 + 5, 5) 2^(-(5 + 5)) = ((5 + 5)!)/(5! 5! 2^(5 + 5)) = 63/256 ≈ 0.2461 ≈ 1/4.063
(assuming children are independent and male and female are equally likely

 

2) | probability
less than 5 boys | 0.377
5 or less boys | 0.623
more than 5 boys | 0.377
5 or more boys | 0.623
(assuming children are independent and male and female are equally likely)

 Jan 5, 2017
 #1
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P(more grandsons than granddaughters or more granddaughters than grandsons)

= 1 - P(equal amount of granddaughters and grandsons)

= 1 - \(\left(\dfrac{1}{2}\right)^{10}\)

\(\dfrac{1023}{1024}\)

By looking at the question, there are clues that you come from China too(Mr WONG!?!?IS IT ME???? LOL). Where you from? Me from Hong Kong.

 Jan 5, 2017
edited by MaxWong  Jan 5, 2017
 #10
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+5

Nope. I am not from china.

arnolde1234  Jan 5, 2017
 #11
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+5

I'm from India

arnolde1234  Jan 5, 2017
 #2
avatar
+10
Best Answer

1) Equal probability of 5 boys and 5 boys =

 

binomial(5 + 5, 5) 2^(-(5 + 5)) = ((5 + 5)!)/(5! 5! 2^(5 + 5)) = 63/256 ≈ 0.2461 ≈ 1/4.063
(assuming children are independent and male and female are equally likely

 

2) | probability
less than 5 boys | 0.377
5 or less boys | 0.623
more than 5 boys | 0.377
5 or more boys | 0.623
(assuming children are independent and male and female are equally likely)

Guest Jan 5, 2017
 #3
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OK....... What is that!?!?

 

binom of (5+5, 5) thing!?!?

 

I just treated it as a simple probability problem!!

MaxWong  Jan 5, 2017
 #12
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+5

binomial(5+5,5) is binomial(10,5) and Can also be written as:

 

10C5

(n,r)C(10,5)......I think that is how u can write it.

 

it means:

 

(n!)/(((n-r)!)r!)

 

so in this case it is:

 

10!/((10-5)!*5!)

10!/(5!*5!)

 

(10*9*8*7*6)/(5*4*3*2)

 

(9*2*7*2) = 252

 

In words it means you have n things and how many ways can u choose r things out of the n.

 

FYI n and r are variables.

 

Here is more in better detail AND LaTeX than me

 

More detail

arnolde1234  Jan 5, 2017
 #13
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+5

Also, the answer is 1 - 63/256 like melody said. 193/256.

arnolde1234  Jan 5, 2017
 #4
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No. 1 above should read " equal probability of 5 boys and 5 girls"

 Jan 5, 2017
 #5
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Ok....... I am not very familiar with probability...... Calculus is my thing!!

MaxWong  Jan 5, 2017
 #6
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+5

No Max: Probability can get very complicated very quickly:

The probability of having 5 boys and 5 girls is computed as follows:

10! /[ 5! x 5! x 2^10] =0.24609375 x 100 =~24.61%

 Jan 5, 2017
 #7
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0

Ok.......

I shouldn't have answered this question.......

MaxWong  Jan 5, 2017
 #8
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Mr. Wong has 10 grandchildren. Assuming that the gender of each child is determined independently and with equal likelihood of male and female, what is the probability that Mr. Wong has more grandsons than granddaughters or more granddaughters than grandsons?

 

1 - (probability of 5 girls and 5 boys)

 

10C5(0.5)^5*(0.5)^5  =  10C5*(0.5)^10 = 0.24609375

 

1-0.24609375 = 0.75390625 = 75%

 Jan 5, 2017
 #9
avatar+118673 
0

Yes Max, Mr Wong is YOU.  The future you!  The prophesy foretells us all, you are to have 10 grandchildren !!

 

Arnolde1234 has said - "Max will multiply" 

 

You always were good with numbers   wink

Melody  Jan 5, 2017

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