Question

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.

Answer 1

Total number of pens = 12 + 132 = 144

total number of good pens = 132

P (getting a good pen) = `"number of favourable outcomes"/"total number of outcomes"`

= `132/144`

= `11/12`