Probability ncert solutions Chapter 15 Exercise 15.1 Question 16
16. 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.
Let E be the event that pen taken out is a good pen.
Number of outcomes favorable to event E=132 (There are 132 good pens)
Total number of possible outcomes=12+132=144 (There are total of 144 pens)
P(E)=(Number of outcomes favorable to event E)/(Total number of possible outcomes)