Question 194910
this says at least 3 boys so we would follow all branches that have 3 or 4 boys and add the probabilities together: out of the Boys portion , we have 3 branches that lead to 3 or more boys
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in the girls part of the tree only one branch leads to 3 or more boys
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.5*.5*.5*.5+.5*.5*.5*.5+.5*.5*.5*.5+.5*.5*.5*.5=.0625+.0625+.0625+.0625=.25
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so a 1 in 4 chance of 3 or more boys
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<img src="http://i11.photobucket.com/albums/a176/jabberstox/soldiers%20of%20fortune/children.jpg">