12 defective pens are accidentally mixed with 132 good ones. One pen is taken out at random.
The probability that the pen is taken out is a good one.
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
The probability that the pen is taken out is a good one= 0.916