Probability Help...Like GBBGBBGGGBGBBGG

G

Gr8fu13

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Feb 13, 2011
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The question is:
The following string of B's and G's was obtained from tossing a quarter 40 times. Heads were listed as B and tails as G. Use this simulation to estimate the probability of two girls being born in succession.

Answer choices are:
A. 1/4
B. 11/40
C. 11/39
D. 10/39

I tried counting the G's that were two in a row and I listed my answer as 1/4 which as wrong. I have one last chance to answer this question so I thought I would seek out help. I counted the number of G's and it is 21. The number of B's is 19. I know the total is 40 but I have no idea were exactly to go from there. My text says nothing about letter probability especially to this length. I wouldn't think the answer could be any with 39 as a denominator because there were 40 coin tossed. I am leaning towards answer B but I am not sure how they would have gotten 11 as a numerator. Any help would be appreciated. Thanks!
 
Sorry about that...The string is:

Bbgggggbggbbgggbggbbbgbbgbbbbggbbggbggbg
 
Gr8fu13 said:
The question is:
The following string of B's and G's was obtained from tossing a quarter 40 times. Heads were listed as B and tails as G. Use this simulation to estimate the probability of two girls being born in succession.
Answer choices are:
A. 1/4
B. 11/40
C. 11/39
D. 10/39
Click to expand...
I suspect that we are somehow thrown into the middle of a solution.
Here is why. There are \(\displaystyle 2^{40}=1099511627776\) strings of \(\displaystyle B's~\&~G's\) of length 40.
Of those only \(\displaystyle 267914296\) ​do not have two consecutive G's.
Thus none of those answers makes any sense.
 
Sequence of GGG

The sequences of GGG I counted as 1. Should this have been 1 1/2?
 
Didn't count each individual G

I counted each set of GG in the string. I see why I was not coming up with 11. I couldn't understand how they came up with 11...Thanks for clarifying:)
 
Not correct:(

It says B is not correct either. Even though I cannot get credit for it, I still would like to know the answer and how they came up with it because it has to be C or D now. Hmmm
 
Gr8fu13 said:
It says B is not correct either. Even though I cannot get credit for it, I still would like to know the answer and how they came up with it because it has to be C or D now. Hmmm
Click to expand...
This is an terribly written question. I think because of that, the given answers are themselves wrong. The (b) option is the only that makes any sense. That is far reach itself.

My first reply to you is based on a standard problem.
"Out ten live births what is the probability of two consecutive births being girls?" The answer there is \(\displaystyle \frac{55}{64}.\)
 
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