SOLUTION: While shooting arrows, William tell can hit an apple 9 out of 10 time.What is the probability that he will be hit exactly 4 out of 7 time?

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 = .9 and q = .1

nCx = 



P(exactly 4 out of 7 time) = 35 (.9)^4(.1)^3 = .0229635