Question 447361

a) probability that single system will detect = .9 =  9/10  



b) probability that none of two system will detect = 1/10 * 1/10 = 1/100

now, probability that at least one of two system will detect the attack

= 1 - 1/100 = 99/100


c)similarly,  probability that none of three system will detect attack = 1/1000


probability that at least one of three will detect the attack = 999/1000