Question 1083199
The Probability(P) that a passenger shows up is 1 - 0.10 = 0.90
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We use the binomial probability formula
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P(k successes out of n trials) = nCk * p^k * (1-p)^(n-k), where n is 125 and nCk = n! / (k! * (n-k)!)
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Note that since the airline sold 125 tickets, then 125 passengers could show up, 
so  n=125
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a) P ( X < or = 120) = 1 - P( k = 121) - P( k = 122) - P(k = 123) - P(k = 124) - P(k = 125) = 1 - 0.004 = 0.996
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b) P ( X < 120 ) = 1 - P( X > or = 120) = 1 - 0.011 = 0.989
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