Question

Choose the most appropriate option.
$12$ 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.

• A. $7/12$
• B. $11/12$
• C. $10/12$
• D. $9/12$

Answer 1

The correct option is B $11/12$

Total number of pens $=$ Total defective pens $+$ Total good pens

$=12+132$

$=144$

Number of good pens $=132$

Probability of getting good pen $=\frac{Numberofgoodpens}{Totalnumberofpens}$

$=\frac{132}{144}$

$=\frac{11}{12}$