A certain type of flashlight requires two type-D batteries, and the flashlight will work only if both its batteries have acceptable voltages. Suppose that 90% of all batteries from a certain supplier have acceptable voltages. Among ten randomly selected flashlights, what is the probability that at least nine will work? What assumptions did you make in the course of answering the question posed?

Answer Step 1 of 2 Given n=10, For 2 batteries P=0.9*0.9 =0.81 q=1-p =1-0.81 =0.19 Let x= no. of batteries working Here X~B(10,0.81) The pmf of binomial distribution is P(x)=(n c(p )(q ), x=0,1,2……..,n