29. Exercise problem XVI

\(12\) 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.

 

The probability that the pen taken out is a good one \(=\) $\frac{i}{i}$.