12 defective pens are accidentally mixed with 132 good ones It is not possible to just look at a pen...........

Quantitative Aptitiude (CLAT) Probability

12 defective pens are accidentally mixed with 132 good ones. It is not possible to just look at a pen and tell whether or not it is defective. One pen is taken out at random from this lot. Determine the probability that the pen taken out is a good one.

7/12

11/12

10/12

9/12

Explanation:

Total pens = 132+12 = 144.
and total good pens = 132.
hence, probability of pen taken out to be a good one is 132/144 = 66/72
=3 3/36 = 11/13(approx.)
Hence, option 2 is the correct answer.