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­Sorry for sound quality hah. Set up one order of 4 boys and 2 girls (each has 1/2 probability). Multiply by the number of different orders:

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can we also do (1/2)^6 x 6!/4!x2! ans comes out to be the same

here the chance of a child being boy or girl is 1/2 and since there are 6 we are looking for BBBBGG and thus (1/2)^6 but to avoid arrangement issues we can multiply by 6!/4!x2!
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The probability that a family with 6 children has exactly four boys is:

A. 1/3
B. 1/64
C. 15/64
D. 3/8
E. none of the above

NOTE: If the probability of a certain event is \(p\) (\(\frac{1}{2}\) in our case), then the probability of it occurring \(k\) times (4 times in our case) in \(n\)-time (6 in our case) sequence is:

\(P = C^k_n*p^k*(1-p)^{n-k}\)

\(P = C^k_n*p^k*(1-p)^{n-k}= C^4_6*(\frac{1}{2})^4*(1-\frac{1}{2})^{6-4}= C^4_6*(\frac{1}{2})^4*(\frac{1}{2})^{2}=\frac{6!}{4!2!}*\frac{1}{2^6}=\frac{15}{64}\)


Consider this:

We are looking for the case BBBBGG, probability of each B or G is \(\frac{1}{2}\), hence \(\frac{1}{2^6}\). But BBBBGG can occur (these letters can be arranged) in \(\frac{6!}{4!2!}\) # of ways. So, the total probability would be \(\frac{6!}{4!2!}*\frac{1}{2^6}=\frac{15}{64}\).

Answer: C.
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This is an unpopular approach but I will disagree with your solutions, I would have marked E, a here is why:
The statement says a family with 6 children it could be 0B6G, 1B5G, ..., 6B0G, so 7 cases... nobody mentions anything about the order in which this family have the children... so the probability would be 1/7
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The probability that a family with 6 children has exactly four boys is:

A. 1/3
B. 1/64
C. 15/64
D. 3/8
E. none of the above
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PocusFocus
This is an unpopular approach but I will disagree with your solutions, I would have marked E, a here is why:
The statement says a family with 6 children it could be 0B6G, 1B5G, ..., 6B0G, so 7 cases... nobody mentions anything about the order in which this family have the children... so the probability would be 1/7


You are misunderstanding the question. It asks about the probability of having 4 boys and 2 girls. Each of the correct solutions in the thread considers the order of BBBBGG. Please review the solutions again.
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