Question 422891
probability that a person catching a cold is .4 i.e P(A) = 4/10

= 2/5


now, probability that not catching a cold i.e P'(A)=  1-2/5 = 3/5


probability that exactly 4 person among 10 will catch a cold 

= 10C4 * (2/5)^4 * (3/5)^6 

= 210 * (16/625) * (729/15625)


try to get the concept...
u r welcome to get any help..