Question 1170300
This is a Poisson distribution with mean 4
look at probability of 0,1,2 particles enter, and the complement is the answer.
p(0)=e^(-4)=0..0183
p(1)=e^(-4)*4^1/1!=0.0733
p(2)=e^(-4)*4^2/2!=0.1465
that sum is 0.2381
at least 3 is 1-0.2381=0.7619, the answer.
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calculator 1-poissoncdf(4,2)ENTER