In a box of 16 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?	Select:  A) 1/6  B) 2/9  C) 6/20  D) 13/20  E) 3/4
Method- 1   There are 9 fine pieces of pen and 3 defective in a lot of 16 pens   i.e. Probability of first pen NOT being defective = (13/16)   i.e. Probability of Second pen NOT being defective = (12/15) [15 pen remaining with 12 defective remaining considering that first was defective]   Probability of Both pen being NON-defective = (12/15)*(13/16) = 13/20   Answer: option 13/20
<result>D</result>
In a box of 16 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?