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 is taken out is a good one.

Answer 1

Numbers of pens = Numbers of defective pens + Numbers of good pens

∴ Total number of pens = 132 + 12 = 144 pens

P (E) = (Number of favourable outcomes) / (Total number of outcomes)

P (picking a good pen) = 132/144 = 11/12 = 0.916

Answer 2

Explanation:

total pens=132+12=144. and total good pens =132. hence, probability of a pen taken out to be a good one is 132/144=66/72=33/36=11/13.