Hi, there--

Problem: 
A diskette manufacturer determined 3% of its diskettes are defective. 2 disks were sold. 
a)What is the probability that both disks sold are defective? 
b)What is the probability that neither one of the disks is defective?


Answer:
These problems are a little bit like coin flip problems. (You flip two coins. What's the 
probability  that both are heads? both are tails?)

a) What is the probability that both diskettes sold are defective?

The probability of choosing a defective diskette is 0.03 (3%).

The total probabilities must add to 1.00. Since there are only two choices, defective or non-
defective, the probability of choosing a non-defective diskette is 0.97 (97%) since 
0.03+0.97=1.00.

The probability of selling two defective diskettes is (0.03)(0.03) = 0.0009 (very unlikely!)

b) What is the probability that neither one of the diskettes is defective?
The probability of selling two non-defective diskettes is (0.97)(0.97) = 0.9409 (quite likely)

Hope this helps! If you still have questions about this, feel free to email me.

Mrs. Figgy
math.in.the.vortex@gmail.com