Question 440136
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Hi
Note: The probability of x successes in n trials is: 
P = nCx* {{{p^x*q^(n-x)}}} where p and q are the probabilities of success and failure respectively. 
In this case p(defective) = 5/80 =.0625    and q = .9375
  nCx = {{{n!/(x!(n-x)!)}}}
randomly take three light bulbs from the box 
P(none are defective) = (.9375)^3 = .824
P(at least one is defective) =  1 - P(none are defective) = 1 -.824 = .176