posted by lilly on .
solving problem the chicago public school system has about 680 schools about 130 of the schools will be closed. if the five schools are chosen at random find the probability that at least three of them willl be closed
You will need to find P(3), P(4), and P(5). Add those values for your probability.
You can use a binomial probability table, or calculate by hand using the following formula:
P(x) = (nCx)(p^x)[q^(n-x)]
x = 3,4,5
n = 5
p = 130/680 = 0.19
q = 1 - p = 1 - 0.19 = 0.81
I'll let you take it from here.