70% of Amerians file their taxes electronically. For a group of 12 American adults who were selected at random, what is the probability that at least five of them file their taxes electronically?

Answer 1

P=P(5)+P(6)+P(7)+P(8)+P(9)+P(10)+P(11)+
P(12)

P(k)=12Ck(0.7)^k(0.3)^(12-k), k=5,6,...,12

You can also find the probability of the opposite event.