Question 354109
(x+y)^20 when x=.2 and y=.8
190x^2y^18+20xy^19+y^20=.206=20.6%  percent of the time does at least one person not get a seat.
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.8*20=16 mean of those who show up.
sqrt(20*.8*.2)=sqrt(3.2)=1.79 standard deviation.
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y^20=.0115 probability all 20 show up.
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Ed