Hi,

Note: The probability of x successes in n trials is: 

P = nCx*  where p and q are the probabilities of success and failure respectively. 

In this case p= .70 and q = .30

nCx = 

P(at least one in four) = 1 - P(none)

                              P(none) = .30^4

P(at least one in four) = 1 - .30^4 = .9919 

Answer by edjones(8007)   (Show Source): You can put this solution on YOUR website!
 1-.7=.3

.3^4=.0081 prob that none have a heart attack.

1-.0081=.9919 the probability that at least one will have had a heart attack.

.

Ed

 

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