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The probability of a new born baby is a boy is 50% and

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The probability of a new born baby is a boy is 50% and

by varun289 » Thu Dec 13, 2012 7:07 am
203. The probability of a new born baby is a boy is 50% and that of a new born baby is a girl is 50%. Ten mothers are going to give birth to ten babies this morning. What is the probability that at least two babies are boys?
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by Jim@StratusPrep » Thu Dec 13, 2012 7:59 am
Probability of at least 2 babies born a boy is 1 - (probability only 0 or 1 is a boy).

Probability that there are no boys = (1/2)^10

Probability that there is just 1 boy = 10 *(1/2)^10 this is because there any one of the 10 mothers can have the boy while the others all have girls.

(1/2)^10 + 10 *(1/2)^10 = 11/(2^10)

Answer is 1 - 11/(2^10)
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by puneetkhurana2000 » Thu Dec 13, 2012 12:09 pm
Probability of at least 2 babies born a boy is same as 1 - (probability of only 0 or 1 boy).

Probability that there are no boys = (1/2)^10

Probability that there is only 1 boy = (10!/9!) * (1/2)^10 ....BGGGGGGGGG can have different orders

Total is (1/2)^10 + 10 * (1/2)^10 = 11/(2^10)

Answer -- [spoiler]1 - 11/(2^10)[/spoiler]
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by varun289 » Thu Dec 13, 2012 11:35 pm
dear JIM , i still did not understand how come 10 in second part ?

why you multiply with 10 to 1/2^10
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