Question 1136999
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The probability that the machine will be working is the probability that NO MORE THAN 3 component fail


    P = P(0) + P(1) + P(2) + P(3) = 


       = {{{(1-0.2)^7}}} + {{{C[7]^1*(1-0.2)^6*0.2}}} + {{{C[7]^2*(1-0.2)^5*0.2^2}}} + {{{C[7]^3*(1-0.2)^4*0.2^3}}} = 


       = {{{0.8^7 + 7*0.8^6*0.2 + ((7*6)/2)*0.8^5*0.2^2 + ((7*6*5)/(1*2*3))*0.8^4*0.2^3}}} = 0.9667 = 96.67%   (approximately).    <U>ANSWER</U>
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