SOLUTION: Assume that only 31% of music files downloaded from Web sites in 2009 were paid for. Suppose that this percentage holds true for such files downloaded this year. Three downloaded m

Algebra ->  Probability-and-statistics -> SOLUTION: Assume that only 31% of music files downloaded from Web sites in 2009 were paid for. Suppose that this percentage holds true for such files downloaded this year. Three downloaded m      Log On


   

Question 1168535: Assume that only 31% of music files downloaded from Web sites in 2009 were paid for. Suppose that this percentage holds true for such files downloaded this year. Three downloaded music files are selected at random.
(a) What is the probability that all three were paid for?
(b) What is the probability that none were paid for? Assume independence of events.
* I'm confused about how to even start this problem :(
Answer by ikleyn(52778) About Me  (Show Source):
You can put this solution on YOUR website!
.

(a)  P = 0.31*0.31*0.31 = 0.31%5E3.                ANSWER


(b)  P = (1-0.31)*(1-0.31)*(1-0.31) = 0.69%5E3.    ANSWER

If you can not compute it mentally, use your calculator.

-----------

The formulas are self-explanatory.

It means that if you have question/questions, look to them attentively and listen what they will tell you.