Question 1144117
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The general solution is  <U>THIS</U> :


     P(exactly n will get the disease) = {{{C[6]^n*0.2^n*(1-0.2)^(6-n)}}}  for n = 0, 1, 2, 3, 4, 5, 6.      (1)



(a)  P(not more than 2 will catch the disease) = P(0) + P(1) + P(2).


     At this point, use the formula (1).  Calculate  P(0), P(1)  and P(2); then add.




(b)  P(4 or more will catch the disease) = P(4) + P(5) + P(6).


     At this point, use the formula (1), again.  Calculate  P(4), P(5)  and P(6); then add.
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Do the rest on your own.