In a box of 7 pencils, a total of 2 are defective. If a customer buys 3 pencils selected at random from the box, what is the probability that neither pencils will be defective?  Choose one.
A) 1/2 B) 1/5 C) 2/3 D) 2/7 E) 1/7
First, there are 5C3 ways you can select 3 good pencils from 4 good ones.   Second, there are 7C3 ways you select 3 pencils from 6 ones in the box.   Then, the probability that neither pen will be defective is: 5C3/7C3=10/35 = 2/7   Answer is 2/7
<result>D</result>
In a box of 7 pencils, a total of 2 are defective. If a customer buys 3 pencils selected at random from the box, what is the probability that neither pencils will be defective?