gorden wrote:

In a box of 12 pens, a total of 3 are defective. If a customer buys 2 pens selected at random from the box, what is the probability that neither pen will be defective?

A. 1/6

B. 2/9

C. 6/11

D. 9/16

E. 3/4

I have another way to solve by using combinations.

First, there are 9C2 ways you can select 2 good pencils from 9 good ones.

Second, there are 12C2 ways you select 2 pencils from 12 ones in the box.

Then, the probability that neither pen will be defective is: 9C2/12C2=6/11

Song of the day: To be with you- David Archuleta