Question

12 defective pens are accidently mixed with 132 good ones. It is not possible to just look at 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 good one.

Answer 1

No. of good pens = 132

No. of defective pens = 12

Total no. of possible outcomes = 12 + 12 {total no of pens}

E ⟶ event of getting a good pen.

No. of favourable outcomes = 132 {132 good pens}

P (E) = (No.of favorable outcomes)/(Total no.of possible outcomes)

∴ P(E) = 132/144 = 66/72 = 33/36 = 11/12